Factual error: The time period of the film is 1932. In the opening title sequence, you see someone playing with Crayola Crayons (I assume it's Scout). One of the Crayons is labeled "Melon". Binney & Smith didn't sell the Melon colored crayon until 1949. Crayons produced from 1903 to 1948 sold for a nickel and contained only eight colors: red, orange, yellow, green, blue, violet, brown, and black.
Factual error: At the beginning of the movie when Jem and Scout boost up Dill to see inside the courtroom, there is no way Dill would be able to reach such a high place with Jem and Scout's hands only going about waist high.
Factual error: Dill said he was from Meridian MS. When the Jem slapped Boo Radley's door and ran he told Dill to tell them about it back in Meridian County. There is no Meridian County in MS. Just the town of Meridian.