- 330 Constantinople (Byzantium) becomes the capital of the Roman Empire
- 1189 Holy Roman Emperor Frederick I Barbarossa and 100,000 crusaders depart Regensburg for the Third Crusade
- 1751 Pennsylvania Hospital founded by Dr. Thomas Bond and Benjamin Franklin
- 1924 Daimler-Motoren-Gesellschaft and Benz & Cie begin their first joint venture (later merge into Mercedes-Benz)
- 1995 In New York City, more than 170 countries decide to extend the Nuclear Nonproliferation Treaty indefinitely and without conditions.
- 2000 India's population officially reaches 1 billion - Astha Arora named India's billionth baby
- 1893 Henri Desgrange establishes world's 1st bicycle world record, travelling 35.325 km an hour
Waltz introduced into English ballrooms. Some observers consider it disgusting and immoral.
On May 11, 1812
- 1963 Prime Minister of Canada John Turner (33) weds Geills McCrae Kilgour (25)
- 1970 Sammy Davis Jr weds Altovise
- 1996 Fashion designer Cynthia Rowley (39) weds retail store designer Bill Keenan (43) at Manhattan City Hall in New York
- 2001 Actress Suzanne Pleshette (64) weds actor Tom Poston (79) at Manhattan's City Hall