When did George Washington become the first President of the US?

On April 30, 1789, George Washington, standing on the balcony of Federal Hall on Wall Street in New York, took his oath of office as the first President of the United States. Born in 1732 into a Virginia planter family, he learned the morals, manners, and body of knowledge requisite for an 18th-century Virginia gentleman.

Source: The White House