Blooper

(at around 1h 18 mins) Eileen and Arthur are in a diner made to look like the one from Edward Hopper's painting "Nighthawks". That painting wasn't created until 1942.

A resemblance to a painting is not necessarily a Goof; many thousands of diners existed at that time, and the odds are pretty good some of them would look similar to the painting. Also, it likely was an homage by director Herbert Ross.

In the classroom, a modern Canadian flag can be seen. It wasn't designed until 1964.

Early on, a sexually frustrated Arthur zips his fly. In 1934 he would have had to button it.

Bar codes on railroad box cars.

A billboard promoting Carole Lombard's La bisbetica innamorata (1936) is seen at various times throughout the picture. That film came out in 1936, but this one takes place in 1934.

While the film is set in 1934, the characters watch Seguendo la flotta (1936) in a movie theater; that film was released in 1936.

When Arthur meets the blind girl, he says that he is traveling from Chicago to Galena, IL. The police later ask about his travels along IL Route 1. IL Route 1 starts in Chicago and runs south, paralleling the Illinois-Indiana border, ending at the Kentucky border. Galena is west of Chicago, in the extreme northwest corner of the state.