Events
- 1775 - American Revolutionary War: Patrick Henry delivers his famous speech -"give me liberty or give me death" at St. John's Church in Richmond, Virginia.
- 1806 - After traveling through the Louisiana Purchase and reaching the Pacific Ocean, explorers Lewis and Clark and their "Corps of Discovery" begin their arduous journey home.
- 1857 - Elisha Otis's first elevator is installed at 488 Broadway New York City.
- 1868 - The University of California is founded in Oakland, California when the Organic Act is signed into law.
- 1889 - Land run: President Benjamin Harrison opens Oklahoma to white settlement starting on April 22.
- 1896 - The Raines Law is passed by the New York State Legislature, restricting Sunday sale of alcohol to hotels
- 1903 - The Wright Brothers apply for a patent on their invention of one of the first successful airplanes.
- 1908 - American diplomat Durham Stevens is attacked by Korean assassins Jeon Myeong-un and Jang In-hwan, leading to his death in hospital two days later
- 1909 - Theodore Roosevelt leaves New York for a post-presidency safari in Africa. The trip is sponsored by the Smithsonian Institution and National Geographic Society.
- 1962 - NS Savannah, the first nuclear-powered cargo-passenger ship, was launched as a showcase for Dwight D. Eisenhower's Atoms for Peace initiative.
- 1965 - NASA launches Gemini 3, the United States' first two-man space flight (crew: Gus Grissom and John Young).
- 1983 - Strategic Defense Initiative: President Ronald Reagan makes his initial proposal to develop technology to intercept enemy missiles.
- 1989 - Stanley Pons and Martin Fleischmann announce cold fusion at the University of Utah.
- 1994 - In an accident that became known as the Green Ramp disaster, a United States Air Force (USAF) F-16 aircraft collides with a USAF C-130 at Pope Air Force Base and then crashes, killing a group of 24 United States Army soldiers on the ground.
- 2003 - In Nasiriyah, Iraq, 11 soldiers of the 507th Maintenance Company as well as 18 U.S. Marines are killed during the first major conflict of Operation Iraqi Freedom.
- 2005 - The United States 11th Circuit Court of Appeals, in a 2-1 decision, refuses to order the reinsertion of Terri Schiavo's feeding tube.
- 2005 - A major explosion at the Texas City Refinery kills 15 workers.
- 2006 - Federal Reserve discontinues publishing M3 money supply.