January 14– U.S. Secretary of the Treasury Alexander Hamilton submits his proposed plan for payment of American debts, starting with $12,000,000 to pay the foreign debts of the confederation, followed by $40 million for domestic debts, and $21.5 million for the war debts of the states. The plan is narrowly approved 14-12 in the Senate, and 34-28 in the House.[2]
January 15 – Fletcher Christian & 8 mutineers aboard the Bounty land on Pitcairn.
Olowalu Massacre: American Captain Simon Metcalfe opens fire with cannon towards villagers in canoes, killing about one hundred Hawaiians, and wounding many others.[3]
March 4– France is divided into 83 départements, which cut across the former provinces, in an attempt to dislodge regional loyalties based on noble ownership of land.
March 6– The New York legislature consents to the admission to the Union of a new state, Vermont, formed within the boundaries of New York, contingent upon the successful conclusion of negotiations concerning disputed real-estate claims, and the boundary between the two states.
May 13–Battle of Reval: Gustav III of Sweden sends the battlefleet to eliminate the Russian squadron wintering at Reval (Estonia), but is defeated; 8 Russians, 130 Swedes are killed, up to 520 captured, 1 ship is burnt, another captured.
May 26– Congress passes an act to govern the creation of states from the "Southwest Territory", from which Tennessee, Alabama, and Mississippi will be formed.[2]
June 9– Royal assent is given to establishment of the port of Milford Haven in Wales.
June 20–Compromise of 1790: Thomas Jefferson, James Madison, and Alexander Hamilton come to an agreement: Madison agrees to not be "strenuous" in opposition for the assumption of state debts by the federal government; Hamilton agrees to support the capital site being above the Potomac.
June 23– The alleged London Monster is arrested in London; he later receives 40 years for 10 assaults.
July 9–Russo-Swedish War–Second Battle of Svensksund: In a massive Baltic Sea battle of 300 ships, the Swedish Navy captures one third of the Russian galley fleet: 304 Swedes are killed, 3,500 Russians killed and 6,000 captured, 51 Russian galleys and other rowing craft are sunk and 22 are taken.
July 10 — The U.S. House of Representatives votes, 32–29 to approve creating the District of Columbia from portions of Maryland and Virginia for the eventual seat of government and national capital.[2]
July 12–French Revolution: The Civil Constitution of the Clergy is passed. This completes the destruction of the monastic orders, legislating out of existence all regular and secular chapters for either sex, abbacies and priorships.
July 16– U.S. President George Washington signs the Residence Act into law, establishing a site along the Potomac River as the District of Columbia and the future site of the capital of the United States. The move comes after the bill is narrowly approved on July 1 by the Senate, 14 to 12, and on July 9 by the House, 32 to 29.[5] At the same time, plans are made to move the national capital from New York to Philadelphia until the Potomac River site can be completed.
October 7– Commissioners appointed by the New York legislature announce the successful conclusion of negotiations between New York and Vermont, concerning disputed real-estate claims, and the consent of New York's legislature to the admission to the Union of the state of Vermont as the 14th State (which was formed within what New York claimed as its territory, under an Order in Council, that King George III issued on July 20, 1764).
October 10– At least 3,000 people die in Algeria when an earthquake and tsunami strikes the city of Oran. The city is destroyed and Spanish forces eventually flee in 1792.[6]
October–December – Vincent Ogé leads a rebellion of freed blacks in Saint-Domingue. The rebellion is suppressed and Ogé executed.
November 24– France's Constituent Assembly passes a law requiring all Roman Catholic priests to swear an oath of acceptance of the new French Constitution.[7]
December 6– The United States Congress opens its first session in the new temporary U.S. capital in Philadelphia.[11]
December 10– The Hawkesbury and Nepean Wars begin in New South Wales, Australia, as a result of deterioration in relations and increasing colonization.
"PHILADELPHIA, December 1", in The Pennsylvania Gazette (Philadelphia), December 1, 1790, p3 ("On Saturday last, at eleven o'clock, A.M., GEORGE WASHINGTON, President of the United States, with his Lady and Family, arrived in this city.")