The newborn foal depicting Secretariat was the incorrect color. The foal used was bay (note the black legs, mane and tail.) Secretariat (aka Big Red) was chestnut, so would not have had black points.
When Penny is being confronted by her brother and husband regarding the inheritance tax. The brother is sitting on the edge of the desk while Penny is sitting on the edge of her chair with her elbows on her knees. As the conversation continues Penny is suddenly sitting upright in the chair with her hands in her lap.
When they are training for the Belmont, Penny Chenery is shown to be turning towards the left to lean her back on the railing while saying her line about how Pancho thinks they are training too hard. The shot cuts to a camera on the left, and we see the whole turn again from that angle.
Eddie Sweat was holding on to Secretariat as he washed him. But when Penny Chenery comes over to help wash him, he's no longer holding onto him, it looks like someone off camera is now holding onto him as you can see the lead moving. And then when Penny moves off towards the foaling shed, Secretariat is now ground tied, no one is holding onto him.
When Penny Chenery asks Miss Ham to talk to trainer Earl Jensen in the stable in private, Miss Ham exits out the stable door, the inside shot shows nothing but a row of windows to the left of the stable doorway. When Miss Ham hides just outside the same stable doorway there are no windows, but there is equipment and hay hanging from the doorway.
In the film the announcer for the Belmont Stakes mentions the margin of victory being 31 lengths which was true, but in real life announcer Chic Anderson announced it as 25 lengths because he was unable to correctly estimate the distance between the horses due to the incredible lead Secretariat had.
In the movie, Secretariat trails the Kentucky Derby field for the first half of the race then stages a dramatic come from behind win. In the real Kentucky Derby, Secretariat was third from last around the first turn and sixth down the back stretch. He made a great charge over the last 3/8 mile but it wasn't quite as dramatic as in the movie.
Penny Chenery meets Ron Turcotte for the first time when looking for a new jockey for Secretariat. In real life, Ron Turcotte had ridden for Penny Chenery many times before, including winning the Kentucky Derby the previous year on Riva Ridge.
In an interview with the Toronto Star, jockey Ron Turcotte says that trainer Lucien Laurin does not golf (he was an avid fisherman) and dresses rather conservatively.
Lucien Laurin berates and fires jockey Paul Feliciano after Secretariat loses his first race. In real life, Feliciano rode Secretariat in his second career start, which he won, before Ron Turcotte replaced him.
In the crowd, in 1973 when Big Red is being brought out to the gates, someone is holding up a sign that says "I 'heart' Red", with the red heart logo. In 1977, William S. Doyle, Deputy Commissioner of the New York State Department of Commerce hired advertising agency Wells Rich Greene to develop a marketing campaign for New York State. Doyle also recruited Milton Glaser, a productive graphic designer to work on the campaign, and created the "I 'heart' NY" design based on Wells Rich Greene's advertising campaign, where it then began the "I 'heart'" popularity across the country and world. Of course, none of this means that it would have been impossible for an "I 'heart' Red" banner to have appeared in 1973.
At the Belmont race the crowd is looking to their left and not following the horses as they progress around the track.
Though taking place between 1969 and 1973, the Chenery children do not age during the course of the film.
In late March 1970, just before Secretariat was born, Penny gets a call at her home in Denver from Eddie that the foal was about to drop. In then next scene her children are playing in the backyard pool, and the leaves on bushes/trees in the yard are green. In late March 1970 the average daily high temperature was below 50 degrees. The trees were bare, and kids most likely weren't swimming in the backyard pool.
When First Call is blown for the Woods Memorial, the trumpeter is shown playing a Monet mouthpiece, first manufactured in 1985.
During the running of the Belmont, the movie shows Secretariat beginning to outrun Sham as the horses straighten down the backstretch. Big Red is depicted as outworking Sham and running at a faster rate . In reality, Secretariat had a longer stride and simply opened up a larger lead with each stride while racing at the same pace as Sham.
In a scene set in 1969, Bull Hancock says Lucien Laurin "dresses like Super Fly (1972)," a 1972 movie.
When Secretariat is led to the track before the Belmont Stakes, someone in the crowd takes his picture with a Kodak Instamatic camera, with a FlipFlash flash device on it. They were first produced in 1975.
When Penny's son John is building a model airplane on the coffee table, he is building the Monogram 1/48 scale Boeing B-29 Superfortress, a kit that wasn't produced until the 1980s.
Before the Belmont Stakes, when Secretariat is being led to the track, someone in the crowd takes his picture with a Kodak Instamatic camera, which would make just one "click" when the picture is taken. The camera makes the sound is that of a single lens reflex (SLR) camera.
As Secretariat is being walked out of the paddock before the Kentucky Derby, a little girl takes his picture. Miss Hamm says, "He's posing again!" but the movement of her lips doesn't match the words she is saying.
In 1969, the family drives to the Virginia farm in a blue 1961 Chevrolet Bel Air with Virginia plates. When they are preparing to leave, the husband says he had the flight moved up. When all except the wife leave, they do so in the same Bel Air. A 1961 car would not have been an airport rental car. It appears they drove from Colorado to Virginia.
The film implies that the Chenery and Hancock farms are close to each other. The Chenery property is in Virginia. Bull and Seth Hancock owned and lived at Claiborne Farm, in Paris, Kentucky.
The police officers at Aqueduct race track wear Nassau County uniforms. Aqueduct is located in Queens, NY, so they should have NYPD uniforms. Belmont Park is located in Nassau County, which is not part of New York City.
In Secretariat's first winning race depicted in the film, the race track announcer refers to the track as "Saratoga Park," but historically Saratoga Race Course has never gone by that name.
When Lucien, Penny and Ronnie are in a restaurant talking about Secretariat being declared Horse of the Year, the cook says he needs more meat because, "These little guys eat like elephants." A jockey's livelihood depends on weighing no more than 120 pounds. Active jockeys exercise obsessively and follow very strict diets.
As a French-Canadian, Lucien's name is pronounced "Loo/see/en". NOT "Looshen"
When Penny and her rival owner trade barbs at a press conference, Penny says the other owner's horse has as much chance of beating Secretariat on the track as he, himself, has of beating Grayson Dodge in the ring. In spring 1973, George Foreman was the boxing champion, and Ali was considered quite vulnerable.