- 1775 – American Revolutionary War: The war begins at the Battle of Lexington and Concord.
- 1943 – World War II: In Poland, German troops enter the Warsaw ghetto to round up the remaining Jews, beginning the Warsaw Ghetto Uprising.
- 1976 – Executive Order 9066 is rescinded.
- 1993- The Government kills 76 people in Waco, TX in revenge for the killing of 4 ATF agents. The original raid was due to the failure to pay taxes on rifles.
- 1995- Murrah Building is bombed by Tim McVeigh in revenge for the Waco killings.
Although not the 19th, the Columbine massacre was carried out the next morning (April 20th)