Cyrus Griffin is probably the "President" you want. He was president of the Continental Congress when the Constitution was ratified June 21, 1788, while Washington didn't take office until April 1789.
John Hancock was the 1st President, of the Continental Congress, in July 4, 1776. He first signed the Declaration of Independence, in very large letters to make sure King George could read it.
Hancock wanted to be the Army commander, but the Continental Congress went with Washington instead. The British made an offer of amnesty to any Americans who laid down arms, but with 2 exceptions, they planned to hang John Hancock and Sam Adams regardless whether they laid down arms or not.
Hancock didn't own slaves. Washington owned 300 slaves. Why don't we recognize Hancock more? Including his being the First President.
Actually there were other presidents of the Continental Congress before Hancock, but that was before the Declaration of Independence Peyton Randolph was the very 1st, also 3rd president of the United States. Hancock was the 4th and 13th president. We had 16 presidents before Washington.