He was one of the committee who, on behalf of the colony, received General Washington when he passed on his way through New York to assume the command of the Continental troops at Boston, already standing in an hostile attitude before Gage and Howe at that city, but at the same time he counselled that all due respect should be paid to Tryon, the Colonial Governor, at New York until the reconciliatory overtures of the New York Congress had been acted on by the home government. But, in the same year, and only a few months later, the course of events drove him forever to the American side. The Declaration of Independence had been adopted by the Continental Congress and Morris's half-brother Lewis was a Representative of New York in that body. All the other States had signed; New York held back for the reason that her delegates had not, under their appointment by the Provincial Legislature, any authority to sign. Gouverneur Morris, on the fioor of the State Legislature, then showed by a masterly argument why for their security the States must declare their independence of foreign rule and our Colonial Legislature after the passage of the Declaration ordered Lewis Morris and the other representatives of that colony to append their signatures to it.

But he had still valuable duties to perform for his native colony, not yet a State. His aged mother had two daughters married to Royalists, and a third had just died. Gouverneur, while serving in the State Congress at Fishkill, received news of his sister's death. His letter to his mother, given at length by Mr. Sparks, is one of the most touching expositions of a struggle between patriotism and filial and fraternal love. He could not leave his post of duty, though he acknowledges it to be his mother's wish that he should.