1920s: The movie industry based in Hollywood develops rapidly, and cinema replaces the theater as a means of mass entertainment. This last decade of the silent movie nurtures stars such as Charlie Chaplin.

Today: Hollywood retains its preeminence as the movie capital of the western world. Going to the movies is the favorite cultural activity of millions of Americans.

1920s: The Volstead Act becomes effective in 1920 and bans the manufacture and sale of intoxicating liquor throughout the United States. Prohibition fails, however, because it is impossible to enforce. Alcohol is sold illegally in bars known as speakeasies. There are several thousand speakeasies in New York alone. Prohibition also produces an increase in organized crime, since large profits can be made from the sale of illegal alcohol.

Today: Alcohol abuse is a significant social problem. Alcohol is a contributing factor in thousands of traffic fatalities...