Found this interesting:
Built in two months on RKO property in Encino, California, Bedford Falls was one of the biggest movie sets constructed in Hollywood’s Golden Age. It covered four acres and included more than 75 buildings, slums, factories, residential neighborhoods and a Main Street that stretched for 300 yards. Twenty full-grown oak trees were transplanted to suggest that the town—said to be based on Seneca Falls, New York—had a long history.
Sure looks like the real thing doesn’t it?