It is the 110th day of the year, with only 255 days remaining until the new year.
1775 - The Siege of Boston begin, following the battles of Lexington and Concord.
1836 - U.S. Congress passes an act creating the Wisconsin Territory.
1861 - Robert E. Lee resigns his commission in the United States Army, in order to command the forces of the state of Virginia.
1862 - Louis Pasteur and Claude Bernard complete the first pasteurization tests.
1902 - Pierre and Marie Curie refine radium chloride.
1912 - Opening Day for baseball's Tiger Stadium in Detroit, Michigan and Fenway Park in Boston, Massachusetts.
1916 - The Chicago Cubs play their first game at Weeghman Park, currently Wrigley Field, defeating the Cincinnati Reds by a score of 7 to 6 in 11 innings.
1918 - Manfred von Richtofen, The Red Baron, shoots down his 79th and 80th victims, his final victories before his death the following day.
1926 - Western Electric and Warner Bros. announce Vitaphone, a process to add sound to film.
1939 - Adolf Hitler's 50th birthday, is celebrated as a national holiday throughout Germany.
1945 - Adolf Hitler makes his last trip to the surface to award Iron Crosses to boy soldiers of the Hitler Youth.
1986 - Pianist Vladimir Horowitz performs in his native Russia for the first time in 61 years.
1999 - In a horrific episode, Eric Harris and Dylan Klebold kill 13 people and injure 24 others before committing suicide at Columbine High School in Jefferson County, Colorado.
2008 - Danica Patrick wins the Indy Japan 300 becoming the first female driver in history to win an Indy car race.
2010 - The Deepwater Horizon oil well explodes in the Gulf of Mexico, killing eleven workers and beginning an oil spill that will last five months.