George Washington took the presidential oath at his first inauguration on April 30, 1789.
The ceremony took place on the balcony of Federal Hall in New York City, then the national capital. Robert R. Livingston, chancellor of New York, administered the oath because the new federal judiciary had not yet been organized. Washington became the first president under the Constitution.
The Constitution had set March 4, 1789, as the beginning of the new government, but logistical delays prevented the executive branch from operating on that date. Congress first needed enough members to conduct business, count the electoral votes, and notify Washington of his election at Mount Vernon.
Washington had been elected unanimously by the Electoral College in the first presidential election and was reelected unanimously in 1792. His first inauguration therefore marked both a personal milestone and the practical launch of the executive branch created by the Constitution.