New York City was the first U.S. capital under the Constitution, before the government moved to Philadelphia.
The new federal government began operating in New York on March 4, 1789. Congress met at Federal Hall on Wall Street, where George Washington took the presidential oath on April 30. The city served as the constitutional capital until August 12, 1790.
Philadelphia then became the temporary capital, remaining the seat of the federal government from 1790 to 1800. The Residence Act of 1790 arranged for a permanent capital on the Potomac River while Philadelphia hosted the government during the transition.
Washington, D.C., became the national capital in 1800. This history can cause confusion because New York and Philadelphia had also hosted earlier Continental Congresses and governments under the Articles of Confederation. The phrase “first capital under the Constitution” specifically identifies New York City, not the first place where revolutionary-era Congresses met.