Not really one person founded Illinois. The reson Illinois is called Illinois today is because of the Illiniwek Confederation. Illinois is the 21st state.

The Native Americans discovered the entire United States as they were here many, many years before us, but they never got recognition for it. Illinois was never officially founded, but was discovered in 1673 by Louis Jolliet and Father Marquette. You can find more information here: http://www.illinois.gov/facts/history.cf...