The Tumultuous Teens.

As the United States entered the second decade of the twentieth century, Americans found themselves in the midst of sweeping economic, political, and cultural changes. The United States began the 1910s as the richest nation in the world, and by the end of the decade it had emerged from World War I with an economic output greater than that of all Europe combined. The United States had also become the most important voice for democratic ideals, but Americans drew back from the responsibility of making those ideals a worldwide reality. A decade that began full of what Herbert Croly called "the promise of American life" ended with a year of labor unrest, race riots, and hysteria over the threat of radicalism. In a decade of causes and crusades — for woman suffrage, Prohibition, the rights of workers — Americans tested the pronouncement of one of the decade's...