Early Twentieth Century: In 1914, Margaret Sanger, a nurse, is prosecuted for publishing The Woman Rebel, a newsletter promoting birth control. The newsletter is banned as obscene literature. Two years later, she opens a birth control clinic in New York City, one of the nation's first. It is illegal in most parts of the United States even for physicians to prescribe or discuss birth control.

Today: Although some religious groups oppose the use of birth control, it is widely available, and generally considered safe and reasonably (but not entirely) effective. Information about sex, conception, and contraception is easily obtained.

Early Twentieth Century: In Pittsburgh, the first American movie theater opens in 1905. Within ten years, all major cities in the United States have cinemas, showing silent spectacles, comedies, and newsreels. By 1912, five million people in the United States go to the movies each day.

Today: Most...