a state in the Middle West of the US; population 12,901,563 (est. 2008); capital, Springfield. It was colonized by the French but was ceded to Britain in 1763. It was acquired by the US in 1783 and became the 21st state in 1818.
Derivatives
Illinoisan
noun & adjective
Illinois in other Oxford dictionaries
Definition of Illinois in the US English dictionary
