1775 - American Revolutionary War: The Battle of Lexington and Concord – British General Thomas Gage attempts to confiscate American colonists' firearms. Captain John Parker orders his band of minutemen to not fire unless fired upon. Random shots rang out among the British soldiers. The minutemen promptly fired back. This was the "shot heard round the world." The British are driven back to Boston, Massachusetts, thus beginning the American Revolutionary War.
1892 - Charles Duryea claims to have driven the first automobile in the United States, in Springfield, Massachusetts.
1938 - RCA–NBC begins regular television broadcasts.
1943 - World War II: In Poland, German troops enter the Warsaw ghetto to round up the remaining Jews, beginning the Warsaw Ghetto Uprising.
1943 - Bicycle Day – Swiss chemist Dr. Albert Hofmann deliberately takes LSD for the first time.
1971 - Charles Manson is sentenced to life in prison for the Sharon Tate murders.
1995 - Oklahoma City bombing: The Alfred P. Murrah Federal Building in Oklahoma City, Oklahoma, USA, is bombed, killing 168.
2005 - Joseph Ratzinger elected Pope Benedict XVI on the second day of the Papal conclave.