Factual error: The Liberty Bell is depicted ringing as the Declaration of Independence is being signed on July 4 (a mistake itself) in the film. The bell actually did not ring on that date, but on July 8, when the Declaration had been returned from the printer and unveiled to the public.
Factual error: When Sally and Bryan are in the street, we can see, at their back, election posters. These posters appeared in 1932, one year after the movie is supposed to take place.