“Here’s looking at you, kid.” The list of unforgettable lines—and the movies that launched them—goes on and on. “Coming Soon,” the largest exhibition of its kind, displays over 200 film posters that range from comedies and musical to thrillers and Westerns. Here is a snapshot history of Hollywood, beginning at the 20th century and ending in the late 80s. Casablanca included. —J.V.