1920s: In the aftermath of World War I, the United States enters an isolationist phase, concerning itself with its own economy and politics, an isolationism that continues until the American entry into World War II in 1941.

1950s: In the aftermath of World War II, the United States engages in the cold war with the Soviet Union, as the country attempts to stop the spread of communism throughout the world.

Today: The Soviet Union no longer exists, and the cold war is now over.

1920s: The stock market booms, and many invest in the stock market, often on credit, undermining the economic stability of the country. In 1929, the good times come to a halt with the stock market crash of October, ushering in the ten long years of the Great Depression that follows.

1950s: As soldiers return home first from World War II and then...