The Funding Act of 1790, the full title of which is An Act making provision for the [payment of the] Debt of the United States, was passed on August 4, 1790, by the United States Congress as part of the Compromise of 1790, to address the issue of funding (debt service, repayment, and retirement) of the domestic debt incurred by the state governments, first as Thirteen Colonies, then as states in rebellion, in independence, in Confederation, and finally as members of a single federal Union. By the Act, the newly-inaugurated federal government under the U.S. Constitution assumed and thereby retired the debts of each of the individual colonies in rebellion and the bonded debts of the States in Confederation, which each state had individually and independently issued on its own "full faith and credit" when each of them was, in effect, an independent nation.
Through the new Department of the Treasury, the U.S. government issued U.S. Treasury Securities backed by the "full faith and credit" of the United States and offered them to the bondholders of the former States' and Confederation's bonded debts at par—that is, at 100% of the state bonds' face value (full assumption) and at rates of interest (and all other terms) that were as specified on the bonds when they were issued by the states and Confederation.
When that was done, "full assumption" of state debts by the federal government had thereby occurred through the issue of federal securities and, for the states of the new Union, the full and complete retirement of their bonded obligations incurred in the Revolution and the Confederation.