George Washington (1789)
The Electoral College elected Washington unanimously in 1789, and again in the 1792 election; he remains the only president to receive 100% of electoral votes. John Adams was elected vice president. Washington took the oath of office as the first President under the Constitution for the United States of America on April 30, 1789 at Federal Hall in New York City although, at first, he had not wanted the position.
Benson John Lossing, ed. Harper's Encyclopedia of United States History (vol. 10) (New York, NY: Harper and Brothers, 1912)