Illinois Country - Post-colonial Period

Post-colonial Period

During the Revolutionary War, General George Rogers Clark took possession of the entire Illinois Country for Virginia. In November 1778, the Virginia legislature created the county of Illinois comprising all of the lands lying west of the Ohio River to which Virginia had any claim, with Kaskaskia as the county seat. Captain John Todd was named as governor. However, this government was limited to the former French settlements and was rather ineffective.

For their assistance to General Clark in the war, French and Indian residents of Illinois Country were given full citizenship. Under the Northwest Ordinance and many subsequent treaties and acts of Congress, the French and Indian residents of Vincennes and Kaskaskia were granted specific exemptions, as they had declared themselves citizens of Virginia. The term Illinois Country was sometimes used in legislation to refer to these settlements.

Much of the Illinois Country region became an organized territory of the United States with the establishment of the Northwest Territory in 1787.

During the 19th century, steamboat travel flourished on the Mississippi River, which was good for the economy of St. Louis and other towns, but it led to deforestation along the river. Adverse environmental effects resulted, including more severe flooding as the river became broader and more shallow, lateral changes in the channel, instability of banks, and loss of towns due to flooding or channel changes. Much of archeological importance was lost in the flooding and destruction of French colonial towns such as Kaskaskia, St. Philippe, and Cahokia, Illinois; and Old Mines and old Ste. Genevieve, Missouri.