Before the Belmont Stakes race, when Secretariat is being led to the track, one of the people in the crowd takes his picture with a Kodak Instamatic camera. It has a FlipFlash flash device on it - these weren't made until 1975.
The family drives to the farm in Virginia, in 1969, 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. It appears they drove (not flew) from Colorado to Virginia, as a 1961 car would not have been a rental at an airport in 1969 due to the age of the car - rentals are always late model cars less than 2-3 years old, so it is unclear how they drove to and from the farm in that car.
The credits note that the Scripture version used at Mrs. Cheney's funeral was New International Version. Mrs. Cheney died in 1969. The NIV Bible was first copyrighted in 1973, and was not in wide-spread use by pastors, etc., until several years later. The version used at the funeral should have most likely been the King James Version, which was widely used by most pastors at that time in most main-stream denominations.
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.
Before the Belmont Stakes race, when Secretariat is being led to the track, one of the people in the crowd takes his picture with a Kodak Instamatic camera which would make just one "click" when the picture is taken yet the sound is that of a single lens reflex (SLR) camera.
When Lucien, Penny and Ronnie are in a restaurant talking about how Secretariat has been declared Horse of the Year, the cook talks about needing more meat because, "These little guys eat like elephants." No active jockey would do that. In fact, they watch their weight so closely that they exercise obsessively and follow very strict diets. Their living depends on them making a weight of no more than 120 pounds, so no active jockey would ever "eat like an elephant".
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's family is watching the Preakness on television at home, after Secretariat wins her son reaches into the bowl of popcorn sitting on the table and throws hands full of popcorn in the air. In all the shots leading up to the win, there is no popcorn on the floor or table, but in the shot where he reaches into the bowl, there is already popcorn scattered all over the table and floor.
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.
During the Kentucky Derby race, stable-hand Eddie Sweat is first seen in a crowded area, apparently under cover. When the horses reach the front stretch, he's seen on the rail in the sun. Then after the finish, he's back under cover in the crowd again.
When the jockeys are mounting their horses prior to the Belmont, Sham's jockey says to Ron Turcotte "You're going to eat dirt today Ronnie." and the crosses his arms as Turcotte walks away and says "I don't think so." under his breath. The next instant Sham's owner is talking to Sham's jockey and his arms are no longer crossed.
When Penny is confronted by her brother and husband regarding the inheritance tax that must be paid she ends up calling Ms. Hamm into the room. When Ms. Hamm enters the door remains open behind her throughout the scene. Then as Ms. Hamm turns to leave she has to open the door to exit.
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.
At Aqueduct race track the police are shown wearing Nassau county uniforms. Aqueduct is located in Queens NY which is part of NYC. The police should be NYC cops. Belmont Park is located in Nassau County NY which is not part of NYC.
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.
Penny Chenery is shown meeting Ron Turcotte for the first time when looking for a new jockey for Secretariat. However, he had ridden for her many times before, including winning the Kentucky Derby the previous year on Riva Ridge.
Lucien Laurin is shown berating and firing jockey Paul Feliciano after Secretariat lost his first race. However, Paul Feliciano did ride Secretariat in his second career start, which he won, before being replaced by Ron Turcotte.
When Secretariat is shown coming around the final turn at the Belmont stakes, there are a number of photographers along the rail taking pictures as he passes. There are three concentric tracks at Belmont with the Belmont Stakes being run on the longest, outer track. There were no people standing on either of the inner tracks and therefore, no photographers along the rail during the actual race.
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.
When the Belmont Stakes is being run, it appears to be in the autumn, as the trees in the background are changing colors. In New York this generally occurs in early to mid-October. The Belmont Stakes is run in June, and the trees should be an intense green.
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.