1898 – Spanish-American War: The United States declares state of war on Spain effective from 21st April.
1901 – New York becomes 1st state requiring automobile license plates ($1 fee)
1914 – US President Woodrow Wilson is persuaded by Argentina, Brazil, and Chili to accept mediation in the conflict with Mexico.
1928 – Buddy, a German Shepherd, becomes 1st guide dog for a US citizen, Morris Frank.
1945 – 45 countries convene UN Conference on Intl Organization in San Francisco.
1945 – “Elve Day” – US and Soviet forces meet at Togau, Germany on the Elbe River during the invasion of Germany in WWII.
1950 – Chuck Cooper becomes the 1st African-American to be drafted into the NBA (for Boston Celtics)
1952 – American Bowling Congress approves use of an automatic pinsetter.
1954 – Bell labs announces the 1st solar battery made from silicon. It has about 6% efficiency.
1959 – St Lawrence Seaway linking Atlantic and the Great Lakes opens to shopping.
1961 – Robert Noyce patents integrated circuit.
1971 – About 200,000 anti-Vietnam War protesters march on Washington, D.C.
1974 – NFL moves goal posts & adopt sudden-death playoff.
1978 – Supreme Court rules pension plans can’t require women to pay more.
1983 – NASA space probe Pioneer 10 travels beyond Pluto’s orbit.
1985 – Roger Miller’s musical “Big River” opens at Eugene O’Neill Theater NYC for 1005 performances.
1993 – NFL Draft: Washington State quarterback Drew Bledsoe first pick by New England Patriots.
2011 – At least 300 people killed in deadliest tornado outbreak in the Southern United States since the 1974 Super Outbreak.
2019 – Former Vice President Joe Biden announces his campaign for president via video.
2019 – Microsoft becomes the third US firm to be listed with a market worth of $1 trillion, after Apple and Amazon.