Fort Kaskaskia State Historic Site 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 . An earthen redoubt . The village of Kaskaskia , Illinois was founded at the mouth of the Kaskaskia River as a missionary post by the Jesuits in 1703 . Soon afterwards , settlers from the Quebec and Louisiana regions began to trickle towards the rich , alluvial farmland of the central Mississippi Valley . 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 . French - speaking pioneers were noted throughout North America for their comparative fairness towards Native Americans . However , as the Kaskaskia settlement grew throughout the 18th century , the local Indians , members of the Illini Confederacy , may have realized that there might not be enough space for everybody . The French settlers raised " Fort Kaskaskia " around 1759 ; the fort stood atop the bluff that looked down upon the frontier village . " Fort Kaskaskia " is not technically a " fort " , but an earthen redoubt . Frontier settlers throughout Woodland North America often built such redoubts as defensive moves during times of threat from Native Americans . In 1763 the French ceded the Illinois country , including Kaskaskia and the redoubt , to Great Britain . The British did not use the redoubt and left Kaskaskia almost defenseless . Kaskaskia continued to exist as a French - speaking village on the Mississippi River frontier . A key strategic location . 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 . Clark and his men marched overland from Fort Massac , near the present - day Metropolis , Illinois , to Kaskaskia . They avoided being sighted by the British or their Native allies and arrived at Kaskaskia on July 4 , 1778 . Most of the Kaskaskia townspeople welcomed them . After facing a threat from a British force at Vincennes , Indiana , Clark and his men used Kaskaskia as their jumping - off place to capture Vincennes in early 1779 . The Americans controlled Kaskaskia and its redoubt throughout the rest of the war , and won legal control of the territory in the 1783 Treaty of Paris . Kaskaskia , Illinois . Following the war , Kaskaskia was part of the United States and the large , French - speaking population became slowly Americanized . Lewis and Clark stopped here in 1803 and recruited many of the professional hunters and sharpshooter s that accompanied them to the Pacific Ocean in their fateful 1804 - 06 expedition . The village served as the only capital of Illinois Territory in 1809 - 1818 , and briefly ( 1818 – 1820 ) as the first capital of the new U . S . state of Illinois following Illinois ' s admission to the Union on December 3 , 1818 . Pierre Menard , a wealthy fur trader who lived across the Kaskaskia River from Kaskaskia at the bottom of the Fort Kaskaskia redoubt , was elected the new state ' s first Lieutenant Governor . Disaster and new life . During much of the 19th century and especially after the American Civil War , the Mississippi River cut through many of its former oxbows and shortened its channel considerably . In 1881 , during a flood , the moving water of the Mississippi " discovered " a much smaller , parallel riverbed , the mouth of the Kaskaskia . Kaskaskia ' s bed was a few feet lower than the Mississippi ' s bed , so the whole river shifted to the new watercourse , cutting across the head of a former oxbow to do so . For the village of Kaskaskia , the river ' s new course was disastrous . Their village had been by the waterfront of the much smaller river ; now the mighty Mississippi was swallowing the town up . Even the village cemeteries were at risk . In an emergency operation , 3 , 000 graves of the departed of Kaskaskia were exhumed and the remains reburied atop the bluff to the east , at the site of old Fort Kaskaskia . The state of Illinois agreed to maintain the site forever as a memorial to the vanished historic village . The fort today . Fort Kaskaskia is a campsite and picnic area overlooking the Mississippi River . The remains of the 18th - century redoubt can be vaguely traced in the earth . The prominent Kaskaskia cemetery recalls the 1881 flood . Due to state budget cuts , the IHPA temporarily closed Fort Kaskaskia to the public from December 2008 until April 2009 .