Capture of Vincennes

In February 1779, George Rogers Clark led Virginia militia and French allies across flooded Illinois country to attack Fort Sackville at Vincennes in the western theater of the Revolution. Clark's force reached Vincennes on February 23, 1779 and compelled Lieutenant Governor Henry Hamilton to surrender the post on February 24, 1779. The capture reversed British control in the Wabash Valley and gave Virginia a stronger claim to the Old Northwest.

The Vincennes campaign intensified the struggle over whether Great Britain or the United States would control the trans-Appalachian interior after 1778. Henry Hamilton had used Vincennes to coordinate British influence with Native nations, while Clark aimed to break that network before it threatened Kentucky settlements. The winter march therefore became a contest over western sovereignty, Native diplomacy, and the future territorial reach of the American republic.

Clark's success strengthened American claims in the West during the Treaty of Paris negotiations in 1783 and supported Virginia's later cession of northwestern lands to Congress. Those developments fed into the Northwest Ordinance of 1787, which created the territorial system that governed the Ohio Valley under the Confederation.