Patrick Culliton's character is referred to as "Clarence Younger" throughout the movie, but credited as "Jim Younger"
The 1871 newspaper headline referencing missionary and explorer David Livingstone incorrectly spells his name as "Livingston".
The Jeff Adams character claims in 1871 that he and Dr. Earnshaw have been sent from the Surgeon General's office in Washington D.C. but this title was first used in 1891.
The time travelers are both established doctors yet neither one of them ever wears a protective face mask to protect them from contracting the disease, which is an unthinkable lapse of judgment for any physician of the 20th century.