The Illinois Territory was under French control until 1763, when it went to the British. The region became US Territory in 1783.
The Illinois-Wabash Company claimed much of Illinois early on. Fort Dearborn [Chicago] was established in 1803. The Illinois Territory was established in 1809. Illinois became the 21st state in 1818 and Kaskaskia was the 1st capital. Two years later, the capital was moved to Vandalia. In 1837, a young legislator named Abraham Lincoln suggested that Springfield become the capital. Chicago would become a major port city on the Great Lakes.
Family connections: The McHughs settled briefly near Galena in the mid-1840s before moving to Wisconsin. The famly would return to live in Chicago from about 1904-11 before heading to Indianapolis. The Crails were in Chicago at that time as well.
Illinois reading: http://www.destination360.com/north-america/us/illinois/history