Yellowstone National Park

national park, United States

By Kenneth Pletcher View Edit History

Full Article

Behold Yellowstone's hot springs and geysers such as Old Faithful and its various large animal
species

Behold Yellowstone's hot springs and geysers such as Old Faithful and its various large animal
species

Overview of Yellowstone National Park, northwest-central United States.

Encyclopædia Britannica, Inc.

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Yellowstone National Park, the oldest, one of the largest, and probably the best-known
national park in the United States. It is situated principally in northwestern Wyoming and
partly in southern Montana and eastern Idaho and includes the greatest concentration of
hydrothermal features in the world. The park was established by the U.S. Congress on March
1, 1872, as the country’s first national park. It is also generally considered to have been the
first national park in the world, though some naturalists and others have argued that there is
evidence that indicates that the creation of Yellowstone was predated by the creation of Bogd
Khan Mountain National Park in Mongolia, which may date from as early as 1778. Yellowstone
was designated a UNESCO biosphere reserve in 1976 and a World Heritage site in 1978. The
park, which forms a squarelike rectangle with an irregular eastern side, is 63 miles (101 km)
from north to south and 54 miles (87 km) from east to west at its widest point and covers an
area of 3,472 square miles (8,992 square km). The John D. Rockefeller, Jr., Memorial Parkway,
an 80-mile (130-km) scenic roadway that was established in 1972, connects Yellowstone with
Grand Teton National Park to the south. In addition, Yellowstone is surrounded by Gallatin
(northwest and north), Custer (northeast), Shoshone (northeast and east), Bridger-Teton
(southeast and south), and Caribou-Targhee (southwest) national forests. Headquarters are at
Mammoth Hot Springs near the northern entrance to the park.

Old Faithful geyser erupting, Upper Geyser Basin, Yellowstone National Park, northwestern
Wyoming, U.S.

Old Faithful geyser erupting, Upper Geyser Basin, Yellowstone National Park, northwestern
Wyoming, U.S.

iStockphoto/Thinkstock

Yellowstone National Park

Yellowstone National Park

Yellowstone National Park, northwest-central United States, designated a UNESCO World

Heritage site in 1978.
Encyclopædia Britannica, Inc.

Natural environment

Geology

Yellowstone is situated in a region that has been volcanically and seismically active for tens of
millions of years. Tectonic movement of the North American Plate has thinned Earth’s crust in
the area, forming a hot spot (a place where a dome of magma, or molten rock, comes close to
the surface). About 2.1 million years ago a subsurface magma dome that had been building up
in the Yellowstone area blew up in one of the world’s most cataclysmic volcanic eruptions.
Some 600 cubic miles (2,500 cubic km) of rock and ash were ejected, equivalent to about 6,000
times the amount of volcanic material that was released during the eruption of Mount Saint
Helens in 1980. (Observations made in the early 21st century indicated that this single
eruption actually consisted of two events about 6,000 years apart: one very large and a second
much smaller one. Subsequent massive eruptions occurred about 1,300,000 and 640,000 years
ago—the last event (consisting in large part of lava flows) producing about two-fifths as much
material as the first one.

Portion of Obsidian Cliff, northwestern Yellowstone National Park, northwestern Wyoming,

U.S.

Portion of Obsidian Cliff, northwestern Yellowstone National Park, northwestern Wyoming,

U.S.

Jim Peaco/U.S. National Park Service

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Each of those eruptions caused the magma dome that had built up to collapse as its contents
were released, leaving an enormous caldera. The present-day Yellowstone Caldera, the
product of the third eruption, is a roughly oval-shaped basin some 30 by 45 miles (50 by 70
km) that occupies the west-central portion of the national park and includes the northern two-
thirds of Yellowstone Lake. Two resurgent magma domes—one just north of and the other just
west of Yellowstone Lake—have been forming in the caldera, and the western dome underlie
many of the park’s best-known hydrothermal features.

Northern end of Yellowstone Lake, within Yellowstone Caldera, Yellowstone National Park,
northwestern Wyoming, U.S.

Northern end of Yellowstone Lake, within Yellowstone Caldera, Yellowstone National Park,
northwestern Wyoming, U.S.

Jim Peaco/U.S. National Park Service

The Yellowstone region is also extremely active seismically. A network of faults associated with
the region’s volcanic history underlies the park’s surface, and the region experiences hundreds
of small earthquakes each year. The great majority of those quakes are of magnitude 2.0 or
less and are not felt by people in the area, but occasionally a more powerful temblor will strike
in the region and have effects in the park. One such event, a deadly quake that struck in 1959
in southern Montana just outside the northwestern corner of the park, affected a number of
hydrothermal features in Yellowstone, including its iconic geyser, Old Faithful.

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Physical features

Yellowstone’s relief is the result of tectonic activity (volcanism and earthquakes) combined
with the erosional actions of ice and water. Most of the park consists of broad volcanic
plateaus with an average elevation of about 7,875 feet (2,400 metres). Three mountain ranges,
each aligned roughly north to south, protrude into the park: the Gallatin Range in the
northwest, the Absaroka Range in the east, and the northern extremity of the Teton Range
along the park’s southwestern boundary. The tallest mountains in the park are in the
Absarokas, where many summits exceed elevations of 10,000 feet (3,050 metres). The range’s
Eagle Peak, on the park’s boundary in the southeast, is the high point, reaching 11,358 feet
(3,462 metres). Aside from its rugged mountains and spectacular deep glacier-carved valleys,
the park has unusual geologic features, including fossil forests, eroded basaltic lava flows, a
black obsidian (volcanic glass) mountain, and odd erosional forms.

Eagle Peak in the Absaroka Range, the highest point in Yellowstone National Park,
northwestern Wyoming, U.S.

Eagle Peak in the Absaroka Range, the highest point in Yellowstone National Park,
northwestern Wyoming, U.S.

R Lake/U.S. National Park Service

Yellowstone is also known for its many scenic lakes and rivers. The park’s largest body of water
is Yellowstone Lake, which, having a surface area of 132 square miles (342 square km) and
lying at an elevation of 7,730 feet (2,356 metres), is the highest mountain lake of its size in
North America. The West Thumb area—a knoblike protrusion of the lake on its west side—was
formed by a relatively small eruption in the caldera about 150,000 years ago. The next largest
lake, Shoshone Lake, lies in the caldera southwest of Yellowstone Lake.

Lower Falls of the Yellowstone River, Yellowstone National Park, northwestern Wyoming, U.S.

Lower Falls of the Yellowstone River, Yellowstone National Park, northwestern Wyoming, U.S.

Scenics of America/PhotoLink/Getty Images

The park’s most extensive drainage system is that of the Yellowstone River, which enters at the
southeast corner, flows generally northward (including through Yellowstone Lake), and exits
near the northwest corner of the park. The river’s Yellowstone Falls, located in the north-
central part of the park, descend in two majestic cascades: the Upper Falls, with a drop of 114
feet (35 metres), and the Lower Falls, with a drop of 308 feet (94 metres). The falls constitute
the western end of the spectacular Grand Canyon of the Yellowstone. There the river has cut a
gorge 19 miles (30 km) long, between 800 and 1,200 feet (240 and 370 metres) deep, and up
to 4,000 feet (1,200 metres) wide. The walls of the canyon, sculpted from decomposed rhyolite
(volcanic rock), are brilliantly coloured in hues of red, pink, yellow, buff, lavender, and white.
Other streams of note include the Snake River, which rises and flows along the park’s southern
boundary before joining the Lewis River and heading south; and the Gallatin and Madison
rivers, both of which rise in and flow through the northwestern part of Yellowstone before
exiting the park and eventually forming (along with the Jefferson River) the Missouri River in
southern Montana.

Grand Canyon of the Yellowstone, north-central Yellowstone National Park, northwestern

Wyoming, U.S.

Grand Canyon of the Yellowstone, north-central Yellowstone National Park, northwestern

Wyoming, U.S.

© magmarcz/Shutterstock.com

Behold near-boiling water spurting from geysers and hot springs in Wyoming's Yellowstone
National Park

Behold near-boiling water spurting from geysers and hot springs in Wyoming's Yellowstone
National Park

Geysers in Yellowstone National Park, northwestern Wyoming, U.S.

Encyclopædia Britannica, Inc.

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Yellowstone’s principal attractions, however, are its some 10,000 hydrothermal features,
which constitute roughly half of all those known in the world. The region’s deeply fractured
crust allows groundwater to seep down to where it makes contact with the magma. The
superheated and mineral-rich water then returns to the surface as steam vents, fumaroles,
colourful hot pools, mud cauldrons, paint pots, hot springs and terraces, hot rivers, and
geysers. It is thought that the constant stream of minor tremors that shake the region act to
keep open the myriad cracks and fissures in the ground that might otherwise become clogged
with minerals precipitating out of the hot water as it cools. Of the park’s more than 300
geysers—greater than half of the world’s total—many erupt to heights of 100 feet (30 metres)
or more. Old Faithful, in west-central Yellowstone, the most famous geyser in the park, erupts
fairly regularly, roughly every 90 minutes with a range of reasonably predictable variability.

Yellowstone National Park: Castle Geyser

Yellowstone National Park: Castle Geyser

Castle Geyser erupting, Upper Geyser Basin, Yellowstone National Park, northwestern
Wyoming.
U.S National Park Service

Yellowstone National Park

Yellowstone National Park

Morning Glory Pool hot spring, Upper Geyser Basin, Yellowstone National Park, northwestern
Wyoming, U.S.

© Ferenc Cegledi/Shutterstock.com

Many of Yellowstone’s noted geysers and other thermal features are located in the western
portion of the park, between Old Faithful and Mammoth Hot Springs some 50 miles (80 km) to
the north. The greatest concentrations are in the Upper Geyser, Midway Geyser, and Lower
Geyser basins that extend northward for about 10 miles (16 km) from Old Faithful. These
include Giantess Geyser near Old Faithful, with a two- to six-month wait between eruptions,
and the deep-blue Morning Glory Pool just to the northwest in the Upper Geyser Basin;
Excelsior Geyser in the Midway Geyser Basin, which rarely erupts but discharges thousands of
gallons of boiling water per minute; and the Fountain Paint Pots in the Lower Geyser Basin,
with pink, plopping mud geysers, fumaroles, and a blue hot-spring pool.

Whirligig Geyser, Norris Geyser Basin, Yellowstone National Park, northwestern Wyoming, U.S.

Whirligig Geyser, Norris Geyser Basin, Yellowstone National Park, northwestern Wyoming, U.S.

Jim Peaco/U.S. National Park Service

Yellowstone National Park: Castle Geyser

Yellowstone National Park: Castle Geyser

Castle Geyser, Yellowstone National Park, Wyoming.

© Kenneth Keifer/Fotolia

Norris Geyser Basin lies roughly midway between the southern hydrothermal area and
Mammoth Hot Springs. It is noted for having some of the hottest and most acidic
hydrothermal features in the park and also includes Steamboat Geyser, which can throw water
to heights of 300 feet (90 metres) and higher and is the world’s highest-erupting geyser.
Mammoth Hot Springs consists of a broad terraced hillside of travertine (calcium carbonate)
deposited there by dozens of hot springs. Among its notable formations are the multicoloured
Minerva Terrace and Angel Terrace, each which consists of dazzling white rock that in many
areas is tinted by microorganisms on the rock.

Travertine terraces at Mammoth Hot Springs, Yellowstone National Park, northwestern

Wyoming, U.S.

Travertine terraces at Mammoth Hot Springs, Yellowstone National Park, northwestern

Wyoming, U.S.

© Jason Maehl/Shutterstock.com
Climate

Yellowstone’s climate can be described as cool temperate and continental. It is also

considerably variable, influenced by the park’s high average elevation, relatively high latitude,
location deep within the continent, and mountainous terrain. In general, the north-central
portion of Yellowstone tends to have wetter summers and drier winters than the rest of the
park, where the moisture regimens are reversed. Temperatures almost always decrease with
elevation gain. Because of Yellowstone’s large area and variegated topography, weather
conditions at different locations within the park can vary widely at any given time. In addition,
conditions can change dramatically in a short period of time at one location.

Grove of aspen trees in autumn, Yellowstone National Park, northwestern Wyoming, U.S.

Grove of aspen trees in autumn, Yellowstone National Park, northwestern Wyoming, U.S.

S. Gniadik/U.S. National Park Service

Summer days are warm and relatively sunny, with daytime temperatures reaching about 80 °F
(27 °C) in July at lower elevations before dropping to nighttime lows in the 40s or 50s F (about
10 °C); temperatures are usually cooler higher in the mountains. Although precipitation totals
in the warm months generally are light, summer afternoon thunderstorms are common.
Winters are cold and snowy, as temperatures rarely rise above the mid-20s F (about −4 °C) and
often drop to 0 °F (−18 °C) or lower at night. Annual precipitation amounts vary with location
and elevation, being lowest in the north (about 10 inches [250 mm]) and highest on the
western slopes of the northern Teton foothills (about 80 inches [2,000 mm]). Snowfall is heavy
in most areas, especially at higher elevations, and typically begins in early autumn and
continues into April or May.

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Plant and animal life

Some 1,350 species of flowering plants (roughly 1,150 of them native) have been identified in
Yellowstone. About four-fifths of the park’s area is forested, and the vast majority of the tree
growth consists of lodgepole pines. Among the several other conifer species in the park are
whitebark pine, found at higher elevations, especially in the Absarokas; and Douglas firs, which
dominate at lower elevations, notably in northern areas. Cottonwoods and willows grow along
streams, and stands of aspens occur in many sections. Hundreds of types of wildflowers thrive
in a variety of habitats. The earliest blossom in April and the latest in September. Common
species include phlox, lupines, cinquefoils, larkspurs, and Indian paintbrushes.

Dense forest of lodgepole pines in the northern portion of Hayden Valley, north-central
Yellowstone National Park, northwestern Wyoming, U.S.

Dense forest of lodgepole pines in the northern portion of Hayden Valley, north-central
Yellowstone National Park, northwestern Wyoming, U.S.

U.S. National Park Service

Wildflowers in a roadside meadow, east-central Yellowstone National Park, northwestern
Wyoming, U.S.

Wildflowers in a roadside meadow, east-central Yellowstone National Park, northwestern

Wyoming, U.S.

Bob Greenburg/U.S. National Park Service

Animal life in Yellowstone is typical of the Rocky Mountain West, and the park boasts the
greatest assemblage of mammals—more than five dozen species—in the United States,
outside of Alaska. Bison (buffalo), the largest of the mammals, were brought back from near
extinction at the beginning of the 20th century. They now constitute several thousand head
divided into two subpopulations that, respectively, inhabit summer breeding grounds in the
Hayden Valley (north-central) and Lamar Valley (northeast) areas of the park. Other large
mammals often seen in Yellowstone include elk (wapiti), mule deer, black bears, foxes, and
coyotes. There are smaller populations of brown (grizzly) bears, bighorn sheep, pronghorns,
mountain goats, and moose. Bobcats are thought to be present throughout the park, but their
numbers are unknown, and there are occasional sightings of lynx and pumas (mountain lions).
Common smaller mammals include badgers, martens, weasels, river otters, hares and rabbits,
shrews, a variety of bats, and many species of small rodents. Wolves were successfully
reintroduced into Yellowstone in 1995 and are now found throughout much of the park.
Beavers have also made a significant comeback, and several hundred live along streams and
lakes, mainly in the northwest, southeast, and southwest.

bison

bison

Bison grazing in Yellowstone National Park, northwestern Wyoming, U.S.

iStockphoto/Thinkstock

Wolves in winter, Yellowstone National Park, northwestern Wyoming, U.S.

Wolves in winter, Yellowstone National Park, northwestern Wyoming, U.S.

Doug Smith/U.S. National Park Service

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More than 300 different species of birds have been identified as living year-round or seasonally
in Yellowstone or migrating through the park in spring and autumn. Roughly half of that total
nest there during the summer. Songbirds and woodpeckers constitute the greatest number of
species. Among the permanent residents are jays, chickadees, nuthatches, ravens, and
waterfowl such as trumpeter swans and Canada geese. Summer breeders of interest include
sandhill cranes, white pelicans, and common loons—with Yellowstone representing one of the
southernmost points that the latter group reaches in North America. The populations of three
of the park’s raptors—bald eagles, ospreys, and peregrine falcons—have made significant
recoveries after having been severely depleted in the mid-20th century. Each species has been
the subject of a long-term study and monitoring program in Yellowstone.

Flock of white pelicans in Yellowstone National Park, northwestern Wyoming, U.S.

Flock of white pelicans in Yellowstone National Park, northwestern Wyoming, U.S.

U.S. National Park Service

Two bald eagles perched in a tree, Lamar Valley, northeastern Yellowstone National Park,
northwestern Wyoming, U.S.

Two bald eagles perched in a tree, Lamar Valley, northeastern Yellowstone National Park,
northwestern Wyoming, U.S.

Jim Peaco/U.S. National Park Service

Most of the park’s lakes and streams have natural fish populations, but many are located
above waterfalls and other impediments and have introduced populations. For decades
Yellowstone’s waterways were stocked with fish—including three indigenous sport species
(cutthroat trout, Arctic grayling, and Rocky Mountain whitefish) and several nonnative species
(mainly trout)—but that practice was ended in the 1950s. Some of the more remote lakes and
streams subsequently reverted to their fishless state. Concerns over depleting stocks of native
sport fish prompted park officials to implement stringent fishing regulations that included a
catch-and-release policy for those species.

Fewer than a dozen reptile and amphibian species are found in Yellowstone, in large part
because of the region’s cold and relatively dry climate. Notable types include prairie
rattlesnakes (Crotalus viridis), the only venomous species in the park; boreal chorus frogs
(Pseudacris triseriata maculata), known for the loud call of the males during breeding season;
and blotched tiger salamanders (Ambystoma tigrinum melanostictum), which are common in
fishless lakes and ponds.

Also of note are the many varieties of thermophiles (heat-tolerant extremophiles) that thrive
in the park’s hydrothermal features and are responsible for many of their distinctive colours.
Prokaryotic types—e.g., varieties of algae and bacteria—can be found in such features as
Norris Geyser Basin and Mammoth Hot Springs, respectively. Thermophilic archaea—which
can survive in the most extreme conditions—are found in features throughout the park,
including Mud Volcano along the Yellowstone River north of Yellowstone Lake, Grand Prismatic
Spring in Midway Geyser Basin, and Roaring Mountain north of the Norris area.

Colourful archaea in Grand Prismatic Spring, Norris Geyser Basin, Yellowstone National Park,
northwestern Wyoming, U.S.
Colourful archaea in Grand Prismatic Spring, Norris Geyser Basin, Yellowstone National Park,
northwestern Wyoming, U.S.

© Kane513/Shutterstock.com

Human imprint

Early history and creation of the park

Archaeological evidence recovered in Yellowstone indicates that there has been a sustained
human presence in the region since sometime after the end of the last glaciation there (about
13,000 to 14,000 years ago), with the oldest artifacts dating to more than 11,000 years ago.
Little is known about those early peoples. Wind River Shoshone (also called Sheep Eaters) are
thought to have arrived in the Yellowstone area about 1400 ce. Many other groups followed,
and those peoples either lived in or near the land now occupied by the park or visited the area
to hunt, trade, or conduct ceremonies.

Artifacts of prehistoric peoples, collected in the Norris Geyser Basin area, Yellowstone National
Park, northwestern Wyoming, U.S.

Artifacts of prehistoric peoples, collected in the Norris Geyser Basin area, Yellowstone National
Park, northwestern Wyoming, U.S.

Tom Pittenger/U.S. National Park Service

First known photograph of Old Faithful geyser erupting, by William Henry Jackson, 1872 print
of an 1871 photograph.

First known photograph of Old Faithful geyser erupting, by William Henry Jackson, 1872 print
of an 1871 photograph.

Photo by William H. Jackson/U.S. National Park Service

The first person of European ancestry to venture into the Yellowstone region was American
trapper and explorer John Colter, who reached the area in 1807–08 after having been a part of
and then leaving the Lewis and Clark Expedition in 1806. Other trappers—including Jim
Bridger, Joseph Meeks, and Osborne Russell—told of seeing the canyon, lake, and geysers. The
first published account of the region was by Daniel Potts, whose letter to his brother vividly
describing Yellowstone Lake and the West Thumb Geyser Basin appeared in a Philadelphia
newspaper in 1827. Another trapper, Warren Angus Ferris, visited Yellowstone and was the
first to use the name geyser for the hydrothermal features there. Ferris, who was a trained
surveyor, prepared a map of the Yellowstone area in 1836. An official government party led by
Capt. William F. Raynolds failed to reach Yellowstone in 1860, but the well-planned Washburn-
Langford-Doane and Hayden expeditions of 1870 and 1871, respectively, undertook thorough
surveys of the region.

Members of the Hayden survey expedition in the Yellowstone region, 1871, photograph by
William Henry Jackson.

Members of the Hayden survey expedition in the Yellowstone region, 1871, photograph by
William Henry Jackson.
William Henry Jackson photo/U.S. National Park Service

Horse-drawn odometer used by the Hayden survey expedition, 1871, photograph by William
Henry Jackson.

Horse-drawn odometer used by the Hayden survey expedition, 1871, photograph by William
Henry Jackson.

Photo by William H. Jackson/U.S. National Park Service

Proposals for the federal government to protect the Yellowstone region had first been voiced
in the mid-1860s, about the same time that such ideas were also being debated for the
Yosemite area in California. Part of the impetus was through Jay Cooke and his Northern
Pacific Railway Company, which was building a rail line from Lake Superior to the Pacific
Northwest that passed just north of Yellowstone. Ferdinand V. Hayden, upon returning from
leading the 1871 survey, had informed Cooke that Yellowstone was commercially suited only
for recreation. Cooke (seeing the potential for tourism), along with returning members of the
1870 and 1871 journeys and others, became strong advocates for the creation of a national
park at Yellowstone. Their cause was helped significantly by the stunning images of the area
created by two members of the 1871 expedition: paintings by Thomas Moran (whose presence
on the trip had been partially funded by Cooke) and photographs by William Henry Jackson
(the official photographer). The U.S. Congress acted quickly to write a bill authorizing the
creation of Yellowstone National Park, which was passed and signed into law by Pres. Ulysses
S. Grant on March 1, 1872—unlike Yosemite, where, initially, a state park was established and
only later was put under federal control.

Tower Falls and Sulphur Mountain, Yellowstone, reproduction of a watercolour painting by

Thomas Moran, published in Ferdinand Vandiveer Hayden's The Yellowstone National Park,
and the Mountain Regions of Portions of Idaho, Nevada, Colorado and Utah (1876).

Tower Falls and Sulphur Mountain, Yellowstone, reproduction of a watercolour painting by

Thomas Moran, published in Ferdinand Vandiveer Hayden's The Yellowstone National Park,
and the Mountain Regions of Portions of Idaho, Nevada, Colorado and Utah (1876).

The Newberry Library, Gift of Everett D. Graff, 1964 (A Britannica Publishing Partner)

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Development of the park

The park’s first superintendent (1872–77), Nathaniel P. Langford (who had been a member of
the 1870 expedition), was largely ineffectual, primarily because Congress allotted no
administrative funds, and he had to find other work and thus was rarely there. His successor,
Philetus W. Norris (1877–82), however, undertook considerable scientific study of the park,
attempted to implement some basic conservation measures, and supervised the construction
of the park’s first headquarters at Mammoth and many of its early roads.

Map of Yellowstone National Park c. 1900, northwest-central United States; from the 10th
edition of the Encyclopædia Britannica.
Map of Yellowstone National Park c. 1900, northwest-central United States; from the 10th
edition of the Encyclopædia Britannica.

Encyclopædia Britannica, Inc.

Travel to and in the park in those early years was arduous and undertaken by only a small
number of hardy adventurers each year. Added to the physical travel challenges at that time
was the ongoing fighting between Native Americans and the U.S. government. The Battle of
the Little Bighorn (June 1876) had taken place only some 150 miles (240 km) to the northeast
of Yellowstone. The following year Chief Joseph and his Nez Percé band traversed Yellowstone
(west-east) in their attempt to evade capture by U.S. troops. They took and briefly held several
park visitors hostage before all escaped or were released.

By the early 1880s, however, the hostilities had largely ended, and the Northern Pacific had
completed its main track to the Pacific. A spur line from it was built southward to near the
park’s northern entrance (just north of park headquarters), and the company began heavily
promoting tourism to Yellowstone. The first hotel in the park (at Mammoth) opened in 1883.
The railway acquired that hotel in 1886 and began building other overnight accommodations
in the park. That same year the U.S. Army took over administration of Yellowstone.

Alice's Adventures in the New Wonderland, brochure and map published by the Northern
Pacific Railway Company to launch its first full season of tourist service to Yellowstone National
Park, 1884.

Alice's Adventures in the New Wonderland, brochure and map published by the Northern
Pacific Railway Company to launch its first full season of tourist service to Yellowstone National
Park, 1884.

The Newberry Library (A Britannica Publishing Partner)

The military was able to improve protection of park properties from vandalism and from
wildlife poachers—notably, stopping the slaughter of bison in the park. It also undertook major
infrastructure improvements, including the construction of Fort Yellowstone at Mammoth (the
structures of which—built between 1890 and 1913—are still used as the park’s headquarters)
and much of the park’s road system. The Union Pacific Railroad completed a line to the park’s
west entrance in 1907, and the following year visitors began arriving at what became West
Yellowstone, Idaho. Private automobiles were first allowed into the park in 1915. Travel to and
within Yellowstone improved considerably in the early 20th century, and the number of
visitors each year increased steadily. More lodging was built to accommodate them, most
notably the magnificent Old Faithful Inn (completed 1904) in the Upper Geyser Basin. Among
the important dignitaries to visit the park in its early decades were Presidents Chester A.
Arthur (1883) and Theodore Roosevelt (1903).

Stagecoach loaded with passengers in front of the Mammoth Hotel, Yellowstone National
Park, northeastern Wyoming, U.S., early 20th century.
Stagecoach loaded with passengers in front of the Mammoth Hotel, Yellowstone National
Park, northeastern Wyoming, U.S., early 20th century.

U.S. National Park Service

Pres. Theodore Roosevelt (left) at Mammoth Hot Springs in 1903, Yellowstone National Park,
northwestern Wyoming, U.S.

Pres. Theodore Roosevelt (left) at Mammoth Hot Springs in 1903, Yellowstone National Park,
northwestern Wyoming, U.S.

Library of Congress, Washington, D.C. (file no. LC-DIG-stereo-1s02124)

With the establishment of the National Park Service (NPS) in 1916, the army relinquished full
administration of Yellowstone to the NPS and its newly created ranger force by 1918. The new
stewards took steps to increase the amount of scientific exploration in the park and to
establish education programs for the growing number of tourists. Park attendance grew
annually until the U.S. entry into World War II in 1941 (with the exception of the first several
years of the Great Depression of the 1930s), exceeding 100,000 for the first time in 1923 and a
half million in 1940 before dropping off drastically during the travel-restricted war years.
Yellowstone’s boundaries were adjusted twice in that period (1929 and 1932), after which the
park reached its present size.

The contemporary park

As automobile travel throughout the country grew dramatically in the postwar period, so too
did Yellowstone’s annual attendance, surpassing the million mark in 1948 and double that in
1965. This great influx of visitors strained the park’s aging infrastructure, and, as part of NPS’s
Mission 66 system-wide renovation program (1955–66), many of Yellowstone’s facilities were
refurbished—notably the Canyon Village complex at Yellowstone Falls. In addition, there has
been an ongoing program to rebuild and widen most of the roadways in the park to
accommodate the heavy car traffic (regular passenger train service ended in 1960). Resource-
management policies adopted in the 1970s included strict bans on feeding wildlife (notably
bears) and greater regulations on fishing, including prohibiting fishing from the famed Fishing
Bridge at the north end of Yellowstone Lake.

Historic Old Faithful Inn (completed 1904), Yellowstone National Park, northwestern Wyoming,
U.S.

Historic Old Faithful Inn (completed 1904), Yellowstone National Park, northwestern Wyoming,
U.S.

U.S. National Park Service

A significant event in Yellowstone’s more recent history was the great fire of 1988 that charred
some two-fifths of the park’s forestlands and nearly reached Old Faithful Inn. The forests
subsequently have recovered, although areas have been subject to damage by insect pests.
Also noteworthy were the reintroduction of wolves in the park, beginning in 1995, and the
growth of the wolf population to some 100 individuals in little more than a decade. Annual
visits to Yellowstone first exceeded three million in 1992 and have hovered on either side of
that mark since then.

Yellowstone National Park: firestorm, 1988

Yellowstone National Park: firestorm, 1988

Firestorm in Yellowstone National Park, northwestern Wyoming, U.S., 1988.

Jeff Henry/National Park Service

Road access to Yellowstone is via entrances in the north, northeast, east, south, and west; a
highway also skirts the northwestern portion of the park. The park itself has about 465 miles
(750 km) of roads, some two-thirds of which are paved. The road linking the north and
northeast entrances stays open year-round, but other park roads close for the winter in early
November and reopen between late April and late May. However, those roads reopen to
authorized over-snow vehicles between December and March. Yellowstone has extensive
facilities for park goers, including nine visitor’s centres (only one of which, at Mammoth, is
open year-round) and nine hotels and lodges. In addition, there are dozens of dining facilities,
service stations, and stores selling food and a variety of other items—most of them
concentrated at Mammoth or at locations along the central loop road. All close for the winter,
except for lodging and some other facilities that reopen in the Old Faithful and Mammoth
areas for the winter season.

Visitor's centre at Mammoth Hot Springs, Yellowstone National Park, northwestern Wyoming,
U.S.

Visitor's centre at Mammoth Hot Springs, Yellowstone National Park, northwestern Wyoming,
U.S.

Jim Peaco/U.S. National Park Service

A dozen developed campgrounds in Yellowstone are maintained by the NPS or by a private

company, and there are more than 300 primitive backcountry campsites that are accessible via
the park’s roughly 1,000 miles (1,600 km) of trails. In addition, some 15 miles (24 km) of
boardwalks are maintained that give visitors access to many of the best-known hydrothermal
features. Hiking, backpacking, camping, fishing, boating, and wildlife watching are popular
outdoor activities, as are cross-country skiing and snowshoeing in winter. A noted hike ascends
a former automobile road up Mount Washburn in the north-centre of the park and affords
spectacular vistas from its 10,243-foot (3,122-metre) summit.

Kenneth Pletcher

Learn More in these related Britannica articles:

chemistry of sedimentary rocks

sedimentary rock: Origin of cherts

 …springs like those of the Yellowstone National Park area of northwestern Wyoming, U.S.,
are also sites of chert deposition. Encrustations of silica, known as sinter or geyserite, are
volumetrically unimpressive but nevertheless are curiosities. The geyser and hot springs
activity at Yellowstone is probably typical, with a subterranean body of…

Louis-Jacques-Mandé Daguerre: View of the Boulevard du Temple, Paris

history of photography: Landscape and architectural documentation

…public land set aside for Yellowstone National Park. The work these and other
photographers of the American West produced usually was made available in several sizes and
formats, from stereographic images to mammoth-sized works.…

Earth's tectonic plates

plate tectonics: Hotspots

…as in the case of Yellowstone National Park in western North America.…

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Continental Divide National Scenic Trail

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Continental Divide National Scenic Trail

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By The Editors of Encyclopaedia Britannica View Edit History

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Continental Divide National Scenic Trail, primitive mountain footpath and equestrian trail in
the western United States that, when complete, will extend from north to south some 3,100
miles (5,000 km), from the border of Canada to the border of Mexico, through a 100-mile-
(160-km-) wide corridor spanning the Continental Divide. The route passes through Montana,
Idaho, Wyoming, Colorado, and New Mexico.

Bear Hat Mountain above Hidden Lake in Glacier National Park, Montana, U.S., along the
northern section of the Continental Divide National Scenic Trail.

Bear Hat Mountain above Hidden Lake in Glacier National Park, Montana, U.S., along the
northern section of the Continental Divide National Scenic Trail.

Ray Atkeson/Encyclopædia Britannica, Inc.

The trail ascends and descends among the peaks of the Rocky Mountains, passing through
dozens of wilderness areas and national forests. The route travels through five biomes, ranging
from tundra to desert. Its northern terminus is Glacier National Park, where it winds among
glacial lakes. It then follows the Idaho-Montana border for 80 miles (130 km), passing
Montana’s Big Hole National Battlefield, and enters northwestern Wyoming past the Old
Faithful geyser in Yellowstone National Park. From there it runs just east of Grand Teton
National Park, travels the spectacular alpine peaks of Colorado—including Rocky Mountain
National Park and the trail’s highest point (14,230 feet [4,337 metres])—and finally yields to
the deserts of New Mexico. A number of historical and cultural sites exist along the route,
including abandoned mining towns, portions of the Oregon Trail, and the 1,000-year-old Zuni-
Acoma trade route across the lava flows of El Malpais National Monument in west-central New
Mexico. The trail is the most rugged, most remote, and least developed of the eight U.S.
national scenic trails, and wildlife such as bald eagles, osprey, pika, mountain goats, mule deer,
pronghorn, moose, bears, bighorn, and elk may be sighted in its vicinity. Plant life ranges from
pine forest to desert cactus. Each year about a dozen people endeavour to hike the entire trail,
which takes about six months.

In 1966 Benton MacKaye, a founder of the Appalachian National Scenic Trail, proposed to the
U.S. Congress the idea of a trail along the Continental Divide. Congress authorized study of the
proposal in 1968 and in 1978 officially designated the Continental Divide National Scenic Trail.
It incorporated about 1,900 miles (3,100 km) of preexisting trails and routes, while some
additional 1,200 miles (1,900 km) were to be acquired to complete the path. Management and
completion of the trail was made the joint responsibility of the U.S. Forest Service, the
National Park Service, and the Bureau of Land Management. By the beginning of the 21st
century, the trail was about 70 percent complete, with most of the unfinished portion in
Wyoming and New Mexico. The longest continuous (and nearly complete) stretch of trail is
from the Canadian border to Yellowstone National Park, a distance of some 800 miles (1,300
km); the trail also is largely complete in Colorado.

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