1832 – Hot Springs National Park in Arkansas was established as a reservation by an act of Congress. Technically, it was the first United States’ National Park.
1841 – The Murders in the Rue Morgue, by Edgar Allen Poe, was published in Graham’s Lady’s and Gentleman’s Magazine. It is considered the first detective story.
1871 – The Third Force Act, also known as the Ku Klux Act, Congress authorized President Ulysses S. Grant to declare martial law in stopping the Ku Klux Klan.
1862 – The first test of pasteurization was completed by Louis Pasteur and Claude Bernard. Jars at a meeting of the French Academy of Sciences.
1912 – Opening day for baseball’s Tiger Stadium in Detroit, Michigan, and Fenway Park in Boston.
1926 – Western Electric and the Warner Brothers film studio officially introduced Vitaphone, a new process that would enable the addition of sound to film.
1940 – Invented by Dr. Vladimir Zworykin at the RCA laboratories, Camden, New Jersey, the first (US) electron misroscope was demonstrated across the Delaware River, in Philadelphia, Pennsylvania.
1964 – The first picturephone transcontinental call was made between New York City and Anaheim, California.
1974 – #1 Hit April 20, 1974 – May 3, 1974: MFSB and The Three Degrees – TSOP
1991 – #1 Hit April 20, 1991 – April 26, 1991: Wilson Phillips – You’re In Love
1999 – At Columbine High School in Littleton, Colorado, students Dylan Klebold and Eric Harris killed 13 people and wounded 23 more before killing themselves.
2002 – #1 Hit April 20, 2002 – June 28, 2002: Ashanti – Foolish
2008 – Danica Patrick became the first woman to win an Indy Car race
2010 – The Deepwater Horizon, run by British Petroleum (BP) drilling rig exploded in the Gulf of Mexico, killing eleven workers.
2013 – #1 Hit April 20, 2013 – April 26, 2013: Bruno Mars – When I Was Your Man