1950s: In 1950, the U.S. produces 6.7 million automobiles and sells over 13 million used automobiles. In 1956, The Federal Aid Highway Act proposes the construction of approximately 42,500 miles of roads, particularly interstate freeways, to connect major cities. The federal government is to pay for 90 percent of the proposed 33.5 billion effort.

1990s: With approximately 70 percent of the Interstate Highway System having been finished by 1976, the system is now essentially complete. In urban centers it provides major arteries for daily commuting traffic. However, it is now worn from use and in need of repair and continuous upgrading.

1952: The U.S. Atomic Energy Commission explodes a hydrogen nuclear fusion bomb at its testing site at the Eniwetok proving grounds in the Pacific. In the following year, the U.S.S.R. will explode a hydrogen bomb designed by Soviet physicist Andrei Sakharov.

1989: The Berlin Wall, built in 1961 and separating...