Fort Kaskaskia State Historic Site is a 200-acre (0.8 km2) park near Chester, Illinois, on a blufftop overlooking the Mississippi River.

It commemorates the vanished frontier town of Old Kaskaskia and the support it gave to George Rogers Clark in the American Revolution.

They built a village and agricultural settlement around the location of the Jesuit mission, a half-circle of bottomland cradled by the Kaskaskia River and by an oxbow of the Mississippi.

Frontier settlers throughout Woodland North America often built such redoubts as defensive moves during times of threat from Native Americans.

In early 1778, George Rogers Clark, eager to defend what was western Virginia and the Kentucky country from attacks by Native Americans allied to the British, led a tiny force down the Ohio River.

Clark hoped to achieve a strategic coup by linking his expeditionary column with the French-speaking settlements of the Mississippi Valley.

Lewis and Clark stopped here in 1803 and recruited many of the professional hunters and sharpshooters that accompanied them to the Pacific Ocean in their fateful 1804–1806 expedition.