In Philadelphia, he was appointed assistant superintendent of finance of the United States, serving under Robert Morris.
He was selected as a Pennsylvania delegate to the Constitutional Convention in 1787.
During the Convention, he was a friend and ally of George Washington and others who favored a strong central government.
 Morris was elected to serve on a committee of five (chaired by William Samuel Johnson) who drafted the final language of the proposed constitution.
Catherine Drinker Bowen, in her 1966 book Miracle at Philadelphia, called Morris the committee's "amanuensis," meaning that it was his pen that was responsible for most of the draft, as well as its final polished form.

It is said by some that Morris was "an aristocrat to the core," who believed that "there never was, nor ever will be a civilized Society without an Aristocracy".
It is also alleged that he thought that common people were incapable of self-government because he feared that the poor would sell their votes to the rich and that voting should be restricted to property owners.
Duff Cooper wrote of Morris that although he "had warmly espoused the cause of the colonists in the American War of Independence, he retained a cynically aristocratic view of life and a profound contempt for democratic theories."

Morris opposed admitting new western states on an equal basis with the existing eastern states, fearing that the interior wilderness could not furnish "enlightened" national statesmen.
Madison's summary of Morris' speech at the Convention, on 11 July 1787, said that his view "relative to the Western Country had not changed his opinion on that head.
Among other objections it must be apparent they would not be able to furnish men equally enlightened, to share in the administration of our common interests."
His reason given for that was regional: "The Busy haunts of men not the remote wilderness, was the proper school of political Talents.
If the Western people get the power into their hands they will ruin the Atlantic interests."
In this fear, he turned out to be in the minority.
Jon Elster has suggested that Morris' attempt to limit the future power of the West was a strategic move designed to limit the power of slaveholding states, because Morris believed that slavery would predominate in new Western states.

At the convention he gave more speeches than any other delegate, a total of 173.
As a matter of principle, he often vigorously defended the right of anyone to practice his chosen religion without interference, and he argued to include such language in the Constitution.
In Philadelphia, he was appointed assistant superintendent of finance of the United States, serving under Robert Morris. He was selected as a Pennsylvania delegate to the Constitutional Convention in 1787. During the Convention, he was a friend and ally of George Washington and others who favored a strong central government.  Morris was elected to serve on a committee of five (chaired by William Samuel Johnson) who drafted the final language of the proposed constitution. Catherine Drinker Bowen, in her 1966 book Miracle at Philadelphia, called Morris the committee's "amanuensis," meaning that it was his pen that was responsible for most of the draft, as well as its final polished form.
It is said by some that Morris was "an aristocrat to the core," who believed that "there never was, nor ever will be a civilized Society without an Aristocracy". It is also alleged that he thought that common people were incapable of self-government because he feared that the poor would sell their votes to the rich and that voting should be restricted to property owners. Duff Cooper wrote of Morris that although he "had warmly espoused the cause of the colonists in the American War of Independence, he retained a cynically aristocratic view of life and a profound contempt for democratic theories."
Morris opposed admitting new western states on an equal basis with the existing eastern states, fearing that the interior wilderness could not furnish "enlightened" national statesmen. Madison's summary of Morris' speech at the Convention, on 11 July 1787, said that his view "relative to the Western Country had not changed his opinion on that head. Among other objections it must be apparent they would not be able to furnish men equally enlightened, to share in the administration of our common interests." His reason given for that was regional: "The Busy haunts of men not the remote wilderness, was the proper school of political Talents. If the Western people get the power into their hands they will ruin the Atlantic interests." In this fear, he turned out to be in the minority. Jon Elster has suggested that Morris' attempt to limit the future power of the West was a strategic move designed to limit the power of slaveholding states, because Morris believed that slavery would predominate in new Western states.
At the convention he gave more speeches than any other delegate, a total of 173. As a matter of principle, he often vigorously defended the right of anyone to practice his chosen religion without interference, and he argued to include such language in the Constitution.
Gouverneur Morris