It is the 137th day of the year, with only 228 days remaining.
1673 - Louis Joliet and Jacques Marquette begin exploring the Mississippi River.
1792 - The New York Stock Exchange is formed.
1902 - Greek archaeologist Valerios Stais discovers the Antikythera mechanism, an ancient mechanical analog computer.
1939 - The Columbia Lions and Princeton Tigers, play in the first televised sporting event in the U.S., a collegiate baseball game in New York City.
1943 - The United States Army contracts with the University of Pennsylvania's Moore School to develop the ENIAC.
1954 - The Supreme Court hands down a unanimous decision in Brown Vs. Board of Education, of Topeka, Kansas.
1973 - Televised hearings begin in the United States Senate, about the Watergate scandal.
1983 - The U.S. Department of Energy declassifies documents showing world's largest mercury pollution event in Oak Ridge, Tennessee, found to be 4.2 million pounds, in response to the Appalachian Observer's Freedom of Information Act request.
2006 - The aircraft carrier USS Oriskany is sunk in the Gulf of Mexico as an artificial reef.
2007 - Trains from North and South Korea cross the 38th Parallel in a test-run agreed by both governments. This is the first time that trains have crossed the Demilitarized Zone in 54 years.