- In Britain, Thomas Clarkson and Granville Sharp formed the "Society for the Abolition of the Slave Trade" with support from John Wesley, Josiah Wedgwood and others.
- January 11 - William Herschel discovers Titania and Oberon, two moons of Uranus.
- February 4 - Shays' Rebellion fails
- May 13 - Captain Arthur Phillip leaves Portsmouth, England with eleven ships full of convicts to establish a penal colony in Australia.
- May 14 - In Philadelphia, Pennsylvania, delegates begin to meet to write a new Constitution for the United States.
- May 25 - In Philadelphia, Pennsylvania, delegates begin to convene a Constitutional Convention to write a new Constitution for the United States (George Washington is presiding).
- June 6 - Franklin College, named for Benjamin Franklin, opens in Lancaster, Pennsylvania. It later merges with Marshall College to become Franklin and Marshall College.
- July 13 - The United States Congress enacts the Northwest Ordinance establishing governing rules for the Northwest Territory. It also establishes procedures for the admission of new states and limits the expansion of slavery.
- August 27 - Launching a forty-five-foot craft on the Delaware River, John Fitch demonstrates the first successful steamboat in the presence of delegates from the Constitutional Convention. Four years later, in 1791, Fitch would be granted a US patent for his design.
- September 17 - United States Constitution adopted
- December 7 - Delaware ratifies the Constitution and becomes the first U.S. state.
- December 12 - Pennsylvania becomes the second U.S. state.
- December 18 - New Jersey becomes the third U.S. state.