Hoover Dam turbines Oct. 26, 1936: The first electric turbine at the Hoover Dam goes into service. The massive dam near Las Vegas provides hydroelectric power, and the dam creates Lake Mead, a primary drinking water source for much of the southwestern U.S. At right, Hoover Dam turbines in 2008.

Oct. 26, 1948: An air inversion traps fumes from a steel mill in the valley town of Donora, Pa . for several days. Twenty people die, and hundreds are hospitalized in a tragedy that becomes an early call for clean air laws.

Oct. 26, 1979: Recreational fisherman Ken Fraser brings in a 1,496-pound bluefin tuna off Nova Scotia. Three decades later, no bigger bluefin has ever been found.

Photo: Wikimedia Commons

This feature is compiled by Peter Dykstra, an MNN contributor and publisher of Environmental Health News and The Daily Climate .