How was the Vice President was initially chosen during Washington's
term?

In 1789, the first presidential election, George Washington was unanimously elected president of the United States. With 69 electoral votes, Washington won the support of each participating elector. No other president since has come into office with a universal mandate to lead.

Between December 15, 1788 and January 10, 1789, the presidential electors were chosen in each of the states. On February 4, 1789, the Electoral College convened. Ten states cast electoral votes: Connecticut, Delaware, Georgia Maryland, Massachusetts, New Hampshire, New Jersey, Pennsylvania, South Carolina, and Virginia. New York, however, failed to field a slate of electors. North Carolina and Rhode Island were unable to participate because they had not yet ratified the Constitution. After a quorum was finally established, the Congress counted and certified the electoral vote count on April 6.