Corrected entry: After the family buries the grandfather, they resume their trip to California. However, they are driving into the rising sun, which is east-bound. Of course this is obviously poetic license, with the sun representing a new beginning, but still wrong.
Corrected entry: In the book, Rosa Sharon is pregnant, but she and her boyfriend are not married. However, the movie wasn't going to be made if her character wasn't married, so this was changed.
Correction: I have read the book, and they are married in the book.
Correction: It's entirely possible that they had to take an eastbound road after the burial to get to a crossroad to be able to get to a westbound highway. There weren't an awful lot of highways in the 30's, and Interstates were years away from completion.