Forrest is arrested in 1981 at the age of 74, which puts his birth year at 1907. But a flashback shows him as a tween breaking out of a juvenile center in 1936--when he would have been 29.
Forrest straightens and tightens John Hunt's necktie, the but next scene shows the tie hanging loose.
During the research scene prior to the bank heist on the roof the armoured car is number #5012. Years later after his prison sentence an armoured car goes past as Forrest and Jewel walk down the street. The exact same armoured car is used ..... also numbered #5012.
During the final chase scene, the police are behind and right next to Forrest, traveling at a high rate of speed. Suddenly, Forrest make a sharp right turn and parks the car. Not a single police car arrives, even though they would have all seen him turn.
During the ride with Spacek after picking her up from her broken truck, the door lock is in the locked position, then unlocked, then locked, and is unlocked every time we see her at the end of that driving scene.
During the St. Louis bank heist the date shown on the banking table is Wed November 11th. Veterans Day has been a federal bank holiday since 1938, and the bank would have been closed. .
Towards the end of the film, it was indicated that the seventh prison from which Forrest escaped was Shawnee Correctional Center in Vienna, Illinois on October 2, 1955. The facility did not, in fact, open until 1984.
In one of the first scenes of the movie set in 1981, you can the green neon lighting outline of the Bank of America Plaza building in downtown Dallas. That building didn't open until 1985.
Besides using the usual movie convention of not using local TV channel numbers for newscasts, the news stories displayed were typical of smaller town station packages and looked more like early seventies news. Dallas TV news departments KDFW, KXAS, KTVT and especially WFAA-TV were high quality operations and WFAA's 1981 operation included many specialized "beat" reporters focusing on detailed investigation of business, crime, medicine, politics and sports.
The real Forrest Tucker was born in 1920, so when he breaks out of a juvenile detention center as a teen, that is accurate. Giving his age as 74 in 1981, however, is not. That event also takes place in 1983, not 1981.
When Forrest drives off the highway into a field to elude Montana police, Numerous tire tracks, presumably from previous takes, are visible.
A pensive Jewel (Sissy Spacek) almost overfills a kettle with water. She then pours some water out and puts the kettle on the stove. She walks around for a bit, and mere seconds later, in the same take, the kettle starts whistling off screen. The amount of water in it would have taken several minutes to even warm up, let alone boil.
Downtown Dallas was a ghost town in 1981. No downtown homes had been built since the 1940s, office vacancy rates were high, most stores had closed in favor of suburban malls.
Tall Downtown Dallas Building with green outline (Currently the Bank of America Building 901 Main Street) wasn't started until 1983, nor finished until 1985.
When Forrest leaves the bank after trying to pay off Jewel's mortgage, he is seen in an overhead shot. Truncated domes are visible on the sidewalk near the street crossing (the 2 yellow panels) The movie takes place in the early 1980s, and truncated domes were not required in the United States until the Americans with Disabilities Act of 1991. They were practically non existent in the U.S. before then.
During the opening scenes while Forrest is eluding the police, the radio dispatcher calls out that he's driving a white 4 door sedan and then a blue 4 door sedan when in fact both cars are clearly 2 door coupes.
Round "American Bank" building identified as Bellmead, Texas may in fact be in nearby Waco, Tx.
At one point, a newscaster says Robert Redford character is 74. Since the film takes place in 1981, he would have been born in 1907, but he is seen escaping a juvenile detention center in 1936, when he would have been 29.