2. To Kill A Mockingbird
If The Grapes of Wrath is a seminal American masterpiece in both book and cinema form, right above it on most lists would be To Kill A Mockingbird. The Harper Lee novel is a classic, but the adaptation starring Gregory Peck and directed by Robert Mulligan is widely considered as one of the top two or three most "important" pictures in American movies. Peck plays Atticus Finch, a lawyer fighting through The Depression in a racially crippled Southern town. He must defend a black man against a bogus rape charge, and he must teach his children about the poison of racism. Mockingbird handles several important issues of the time with a great eye for detail and an unforgettable performance from Peck, who would go on to win the Academy Award.