1930s: Following an active policy of inclusion, the Communist party recruits many black leaders and thinkers.

1952: A "witch-hunt" for communists begun by U.S. Senator Joseph McCarthy continues through the early 1950s and rums many careers. Today: The 1980s see the collapse of communism in Eastern Europe. In America, politics is increasingly middle-of-the-road. American communists are a small fringe group.

1930s: The U.S. labor movement gains support under the New Deal, but prejudice against African Americans is widespread.

1952: Union membership peaks in 1945 at 35.5% of the non-agricultural workforce and is still strong in the 1950s.

Today: Unions are fully integrated but membership is at an all-time low, and unions are forced to compromise on wages and benefits to preserve jobs.

1930s: Brain surgery to correct the behavior of mentally ill patients, or lobotomy, is widely practiced between 1936 and 1956.

1952: Lobotomy is largely abandoned in favor...