In 1787, Carroll was named a Maryland delegate to the Philadelphia Convention, which convened to revise the Articles, and produced the Constitution. Like his good friend
James Madison of Virginia, Carroll was convinced that a strong central government was needed to regulate commerce among the states and with other nations. He also spoke out repeatedly in opposition to the payment of members of the
United States Congress by the states, reasoning that such compensation would sabotage the strength of the new government because "the dependence of both Houses on the state Legislatures would be complete ... The new government in this form is nothing more than a second edition of [the Continental] Congress in two volumes, instead of one, and perhaps with very few amendments." When it was suggested that the president (executive branch) should be elected by the Congress (legislative branch), Carroll, seconded by
James Wilson, moved that the words "by the legislature" be replaced with "by the people". He and
Thomas Fitzsimons were the only Catholics to sign the Constitution, but their presence was a sign of the continued advancement of religious freedom in America. Carroll played an essential role in formulating the limitation of the powers of the federal or central government. He was the author of the presumption—enshrined in the Constitution as a closing article – that powers not specifically delegated to the federal government were reserved to the states or to the people. Carroll spoke about 20 times during the summer of debates at the Constitutional Convention and served on the Committee on Postponed Matters. Returning to Maryland after the convention, he campaigned for ratification of the Constitution but was not a delegate to the Maryland state convention for ratification. ==Political career==