George Rogers Clark and the American Conquest of the Northwest Territory, 1778-1783

Map of the Northwest Territory by Wikimedia Commons user Jengod

The size of our country practically doubled at the end of the American Revolutionary War thanks to the leadership and persistence of George Rogers Clark in Illinois. Born in 1752 near Charlottesville, Virginia, the hometown of Thomas Jefferson, Clark was in his early twenties when he began his campaign to thwart the British on the northwestern frontier. Five of Clark’s six brothers also served as officers in the American Revolutionary War. His youngest brother William was too young to fight, but later served with Captain Meriwether Lewis in leading the Lewis and Clark Expedition in 1803.

Statue of George Rogers Clark by Hermon Atkins MacNeil, photographed by Einar Einarsson Kvaran

Following the French surrender of Fort de Chartres in 1765 after the end of the French and Indian War, Britain controlled Illinois little more than a decade. When the American Revolutionary War began, British officers received orders to encourage and supply Native American attacks on frontier settlers in what is now Pennsylvania, Virginia, and Kentucky.

George Rogers Clark had grown up on the frontier and was concerned for its welfare and prosperity. Working as a surveyor in the wilderness, he had learned about Native American customs. Suspecting British involvement in the Native American incursions, Clark sent two spies to Illinois. With their report, he convinced Virginia Governor Patrick Henry to authorize a militia to capture the regional forts supplying the attacks. In 1778, Clark’s force of about 175 men traveled down the Ohio River from what is now Louisville, Kentucky, landing at deserted Fort Massac.

Armed with knowledge of a recent alliance between France and the United States and intelligence about Kaskaskia and trails from captured hunters, Clark marched overland to take Kaskaskia by surprise at night on July 4, 1778. The British military had departed, leaving the fort guarded only by a sleeping French commander. While one division was taking the fort, another was securing and disarming the village.

Charcoal drawing of Father Pierre Gibault by Jude Huck, circa 1909, from the Missouri Historical Society

By sharing news of the French alliance and assuring freedom of religion, Clark convinced influential French Jesuit priest Pierre Gibault and the villagers of Kaskaskia to take an oath of allegiance to Virginia. With Father Gibault’s help, Clark immediately formed a company of volunteer French militia and captured Cahokia without much resistance on July 6, 1778.

Father Gibault further informed Clark that the commander of Fort Sackville at Vincennes was away in Detroit. Clark sent him to Vincennes with Captain Leonard Helm to convince the villagers to join them in fighting the British. After pledging an oath of allegiance to Virginia, the people of Vincennes organized a militia and easily took possession of the understaffed fort.

In September, 1778, Clark met with Native Americans in council at Cahokia, making treaties with a number of tribes. News of Clark’s successes prompted Virginia to extend civil government over the region, creating the county of Illinois in November, 1778.

Statue of Francis Vigo by sculptor John Angel, near the George Rogers Clark Memorial on the Wabash River in Vincennes, Indiana, photographed by Wikimedia Commons user Danieljackson

When word of the capture of Vincennes reached Detroit, British Lieutenant Governor Henry Hamilton launched an expedition to retake Fort Sackville, arriving in December, 1778. Lacking a disciplined militia, Captain Helm surrendered the fort to Hamilton. Helm was imprisoned and Father Gibault was prevented from leaving.

St. Louis merchant and former Spanish Army Colonel Francis Vigo offered to visit Vincennes to gather intelligence. Vigo was captured by Hamilton’s Native American allies, but Father Gibault secured his release by organizing the villagers of Vincennes to refuse to supply the fort. After promising to return directly to St. Louis, Vigo traveled to Kaskaskia in January, 1779 to report the extent of Hamilton’s force and munitions, the assistance Clark could expect from the French villagers, and Hamilton’s plans to attack Clark at Kaskaskia in spring.

Vigo’s report propelled Kaskaskia into action. While Clark’s forces made their way east overland to Vincennes, a large boat carrying artillery and supplies traveled on a southern route along the rivers. Clark’s army of two French companies and reenlisted Virginians numbered just 170 men.

Painting of George Rogers Clark’s march to Vincennes by Frederick C. Yohn

Among the hardships of winter travel, forty-five miles from Vincennes, the army had to cross five miles of flooded bottomland between Big Muddy creek and the Little Wabash that was too deep for wading. The flooded Wabash less than ten miles from Vincennes posed another challenge. They had run out of food by that time and had to build their own boats over the course of three days. While preparing to cross the Wabash, they captured five Frenchmen from Vincennes who confirmed that the fort did not know about their approach. After crossing the Wabash, they had to wade through icy water up to their shoulders as they approached Vincennes. Four miles from Vincennes, they restored the health of the weakest with provisions from a captured Native American canoe.

Painting of the fall of Fort Sackville at Vincennes by Frederick C. Yohn, from the Indiana Historical Bureau

Reaching Vincennes after dark, the main army occupied the village while a detachment of fourteen men attacked the fort. Using ammunition the villagers had hidden from the British, the detachment bombarded the fort all night long. After Hamilton declined to surrender during a morning cease-fire, Clark renewed his attack until the afternoon, when he negotiated the fort’s surrender. Assuming Clark’s forces to be great because of the ferocity of their attack, Hamilton was shocked to learn he had been defeated by such a small band. Stores in the fort and provisions enroute from Detroit afforded desperately needed supplies to Clark’s troops while they waited for their boat from the south.

Although Clark wanted to press on to capture Detroit, he instead made treaties with neighboring tribes and returned in March, 1779 to Kaskaskia. Governor Thomas Jefferson asked Clark to construct a fort below the mouth of the Ohio River, which was finished by June, 1780. Afterward, Clark helped defend Virginia from attack by Benedict Arnold and continued to menace British interests in Illinois. Clark’s relentless attacks ultimately convinced the British to cede land in the 1783 Treaty of Paris that became the Northwest Territory.