Factual error: When Meryl Streep is walking outside and talking to Mrs. Miller about the potential abuses of her son, you can see a basketball court in the background and on the court is a 3-point line. The movie is supposed to take place in 1964 and the 3 point line wasn't introduced until 1979/1980.
Factual error: At the beginning of the movie, there is a scene showing a car driving through an intersection containing curb cuts (street-level curb corners) and painted crosswalks. The movie is supposed to be set in 1964. Curb cuts were first introduced in 1970 and not widely used until after the Americans with Disabilities Act of 1990. Painted crosswalks were not used much until the late 1990s.