On this date in history:
In 1896, the U.S. Supreme Court handed down the Plessy vs. Ferguson decision that determined "separate but equal" racial policies are constitutional.
In 1917, President Wilson signed the Selective Service Act of 1917 by which the United States raised an army for service in Europe during World War I.
In 1933, the U.S. Congress created the Tennessee Valley Authority for flood control and rural electrification.
In 1944, Allied troops captured Monte Cassino in Italy after one of the longest and bloodiest battles of World War II.
In 1980, Mount St. Helens in southwestern Washington state erupted, blowing the top off the mountain and killing 57 people.
In 1990, East and West Germany signed a treaty for economic, monetary and social union. West German Chancellor Helmut Kohl said the pact marked the "birth of a free and unified Germany."
In 1991, chemist Helen Sharman became the first Briton in space when she blasted off from the Baikonur Cosmodrome aboard a Soviet spacecraft.
In 1992, bandleader Lawrence Welk, whose bubbly champagne dance music brought him wide popularity, died at age 89.
In 2009, the Hubble Space Telescope was returned to orbit after astronauts finished five spacewalks in a mission to repair and refurbish the 19-year-old instrument.
In 2012, Facebook Inc. had its first day of public trading.
In 2014, AT&T announced it agreed to buy DirecTV for $48.5 billion. The purchase went through in July 2015.