Illinois is an average-sized state. It ranks 25th in America in area. Illinois' total area is 57,918 square miles. 2,325 square miles of this area is covered by water. Most of the water area of Illinois is comprised of the state's slice of Lake Michigan. Illinois is 310 miles long at its longest point and 210 miles wide at its widest point.
How big is Illinois by population?
Though Illinois is only average in area, it is one of the most populated states in the country. Its total population is estimated to be over 12.8 million people. This means that Illinois is the sixth most populous state in America. The greater Chicago area is where around two-thirds of the state's residents live. Unsurprisingly, Chicago is the state's most populous city, with over 2.7 million people living within the city's boundaries. The Chicago area, commonly known as Chicagoland, is home to over 9.6 million people.
The most populous city in Illinois outside of the Chicago area is Rockford, which has a population of around 150,000 people. Spingfield, the state's capital, has a population of around 120,000 people. Bellevile, which is part of the St. Louis area, is the most populous city in southern Illinois with over 44,000 residents.