Place: Philadelphia, Pennsylvania
Following the Land Ordinance of 1785, the U.S. Congress under the Articles of Confederation passed the Northwest Ordinance in 1787. It created the Northwest Territory and specified how it would be governed. One of its most noteworthy elements was a clause prohibiting slavery in the territory and in any states that might arise from it. Although slavery persisted to a limited extent in the region for decades afterward, the Northwest Ordinance nevertheless set a precedent of limiting slavery's expansion in the northern United States, which was subsequently reflected in the Missouri Compromise. The ordinance also detailed the rules of admission for new states, which remained largely unaltered throughout the nation's westward expansion. Though Congress enacted the ordinance while still under the Articles of Confederation, Congress, in 1789, reaffirmed the ordinance in order to make its provisions compatible with the new Constitution.
Peter D. Onuf, Statehood and Union: A History of the Northwest Ordinance (Bloomington: Indiana University Press, 1987).