Peyton R. would have a claim, but the US wasn’t independent then, was it?
If we became independent with the D of I, at the end of the meeting it was Hancock. Hanson has a claim too, for he was the first President of a “perpetual Union”. GW was the first President under the current Constitution. Not a bad thing, not a bad thing at all, esp. having served as President of the Constitutional Convention that worked to write said Constitution.
The separation into Judicial, Executive and Legislative was a significant innovation of the current constitution. UK Parliment still has the Prime Minister elected as just another legislator, and he selects his cabinet from other elected legislators.
You wrote “2 to 16”. Randolph was the 1st of those 16, not Hancock.