Fort Sackville and the Conquest of the Northwest

You are approaching Vincennes, Indiana, and the place where one of the most audacious gambles of the American Revolution paid off in the dead of winter, reshaping the boundaries of the new nation before it had even finished winning its independence.

Vincennes began as a French fur-trading post on the Wabash River, established around seventeen thirty-two and named for a French commander, François-Marie Bissot, sieur de Vincennes. It passed to the British after the French and Indian War, and by the time of the Revolution the British built a stockade here called Fort Sackville, a key link in their chain of western posts stretching from Detroit down through the Illinois country. Control of that chain meant control of the Ohio Valley and, potentially, the entire western frontier.

In the summer of seventeen seventy-eight, Virginia Lieutenant Colonel George Rogers Clark, barely twenty-five years old, led a ragged force of about one hundred seventy-five men on a secret mission authorized by Governor Patrick Henry. Clark took the British posts at Kaskaskia and Cahokia in Illinois without a shot. Fort Sackville fell to his man Captain Leonard Helm. Then, in December, the British Lieutenant Governor Henry Hamilton, known among frontier settlers as the Hair Buyer for allegedly paying bounties on American scalps, marched south from Detroit and retook the fort. Helm surrendered. Hamilton settled in for the winter, assuming no one would dare attack until spring.

Clark attacked in February. He marched one hundred eighty miles through flooded winter prairie, his men wading chest-deep through icy floodwaters for days at a stretch. They arrived at Vincennes on February twenty-third, seventeen seventy-nine. After two days of siege, Hamilton surrendered Fort Sackville on February twenty-fifth. Clark sent Hamilton to Virginia in chains.

That victory gave the United States its legal claim to the entire Northwest Territory, the land that would become Ohio, Indiana, Illinois, Michigan, and Wisconsin. Today the site is marked by the George Rogers Clark National Historical Park, whose granite memorial was dedicated in nineteen thirty-six by President Franklin Roosevelt.