1960s: Fidel Castro's rule in Cuba reminds Americans that communism is "only 90 miles away." President Kennedy and Soviet premier Nikita Kruschev spar over the missiles in Cuba, averting open hostilities only when Kruschev orders the removal of the weapons from that island nation.

Today: Although Castro remains in power, and the U.S. sanctions against him are still in effect, the fall of Russia's communist government effectively ended the Cold War. Cuba is no longer considered a threat to the United States.

1960s: In 1962, Rachel Carson publishes The Silent Spring, the seminal work in the environmental movement. The federal government begins taking steps to protect the environment from further damage. The first landmark legislation is the Clean Air Act of 1963.

Today: Environmental concerns have grown considerably since the 1960s. Most recent studies concern global warming and the population explosion. Bleak predictions about future inability...