1970s: The last American troops leave Vietnam as North Vietnamese troops complete their Communist takeover of South Vietnam. The unpopular, largely unsupported conflict costs more than 56,000 American lives and sharply divides the country at home.

Today: American troops in Afghanistan and other hotbeds of terrorism throughout the world are greatly supported by their own nation and many others, as countries across the globe unite in the war on terrorism.

1970s: The world's last known case of smallpox appears in Somalia, and the deadly disease is considered eradicated when it does not appear for two more years.

Today: Pharmaceutical researchers scramble to create smallpox vaccines to protect Americans from the threat of biological terrorism in the wake of the September 11, 2001, attacks on the World Trade Center and the Pentagon and subsequent cases of anthrax poisonings.

1970s: In a sorrowful and bizarre religious cult display, Jim...