[112] He advised the formation of the Committee of the States to fill the power vacuum when Congress was in recess.[113] The Committee met when Congress adjourned, but disagreements rendered it dysfunctional.[114]
In the Congress's 1783–1784 session, Jefferson acted as chairman of committees to establish a viable system of government for the new Republic and to propose a policy for the settlement of the western territories. He was the principal author of the Land Ordinance of 1784, whereby Virginia ceded to the national government the vast area that it claimed northwest of the Ohio River. He insisted that this territory should not be used as colonial territory by any of the thirteen states, but that it should be divided into sections that could become states. He plotted borders for nine new states in their initial stages and wrote an ordinance banning slavery in all the nation's territories. Congress made extensive revisions, and rejected the ban on slavery.[115][116] The provisions banning slavery, known as the "Jefferson Proviso," were modified and implemented three years later in the Northwest Ordinance of 1787 and became the law for the entire Northwest.