The United States entered the twentieth century during a period of sweeping change. In fact, change and transformation were the norm in the first decade of what has since become known as the "American Century." The United States came to be the leading economic and military power in the world. American democracy became the model for political reform in countries around the world. American publishers, musicians, artists, film makers, and performers of all sorts participated in an outpouring of work that made American popular culture the popular culture of much of the Western world.

The social and economic changes that were sweeping the country were striking. Although it had once been a nation of small towns, rapid changes in living styles led to the concentration of more and more Americans into cities; by 1910, fully 54 percent of the population lived in urban areas. The ethnic...