For years all immigrants were allowed into the U.S., but some could not become citizens. Later, certain nationalities were limited or completely banned. This episode outlines those changes through the 1980s and discusses the pseudoscience of eugenics and how it was used to justify such bigotry and even involuntary sterilizations in the 20th Century.

Within 30 years in the late 1800s and early 1900s, Europe went from controlling 20% of Africa to 90%. It was called "the Scramble for Africa". Find out why Europeans colonized the Americas easily through unintentional germ warfare, but Africa was "the White Man's Grave". Discover how Europe finally conquered Africa; the horrors of the Congo; and the residual problems in Africa which exist today.

Adolf Hitler's insane and evil policies changed the world more than anybody since Christopher Columbus. This episode details the horrors of World War II; explains how Hitler is to blame for the war; illustrates how Hitler made WWII even worse than other wars; and analyzes the effects of WWII for the remainder of the 20th Century and today.

It was the bloodiest battle ever in the Western Hemisphere. For 3 days in July 1863 Americans slaughtered each other on a terrible scale around a small town in Pennsylvania, where the honored dead "gave the last full measure of devotion".

Find out why Robert E. Lee invaded the north, and why he failed so terribly; why the civil war dragged on for almost two more years after this union victory; and how this conflict inspired one of the greatest speeches ever in the English language.

Galileo is considered the father of modern science. His discoveries included the laws of pendulums which led to the development of the first accurate clocks. But tragically, he was tried by the Inquisition of Rome for heresy. The science deniers of the Church threatened to burn him at the stake unless he recanted his claims that he could prove that Copernicus was right: that the Earth is not the center of the universe, that we live in a heliocentric system where the earth and the other planets revolve around the sun.

A lot of elements contributed into winning World War II: Britain refusing to make peace with Nazi Germany after the fall of France along with the Chinese and Soviets willingness to suffer millions of deaths. But World War II was a war between the factories; whichever side could produce the most military equipment would win. The deciding factor in World War II was the fantastic industrial output of the U.S.

Polio was one of the scourges of the 20th century. And it mainly struck children. All of a sudden a person contracted polio and suffered terribly for several days; sometimes they recovered, sometimes they died, and sometimes they were left permanently disabled. The most famous polio victim of all time, Franklin Roosevelt, hid his disability from the public. But this story has a true hero: Jonas Salk, who developed a vaccine which led to the almost complete eradication of this dreaded disease. And Dr. Salk never patented the vaccine or earned any money from his discovery.

Wars are never solely military questions. They always involve politics and the will of the people. This episode outlines America's war in Vietnam and explains why the U.S. lost, including the limitations imposed by the American public and the realities of the Cold War.