It is a little known fact that in July/August 1978 AFI created a list of 50 greatest American films for The Saturday Evening Post, for a special 50 years of talking pictures edition. Except for a top ten, the list was in alphabetical order. The top ten were:
The African Queen (1951)
Casablanca (1942)
Citizen Kane (1941)
Gone With The Wind (1939)
The Grapes of Wrath (1940)
One Flew Over the Cuckoo's Nest (1975)
Singin' in the Rain (1952)
Star Wars (1977)
2001: A Space Odyssey (1968)
The Wizard of Oz (1939)