Illinois vs Missouri

The two states, county by county

Both maps share one density scale, so the same shade means the same number of people per square mile on either side of the border. Darker counties are denser. Select a county to open its page.

Side by side

Population and density

Illinois has 12,710,158 residents, 2.0 times Missouri's 6,245,466. Illinois ranks 6th and Missouri 19th of the 50 states and DC. Illinois is the more crowded, with 229.0 people per square mile against 90.8, 2.5 times.

Land area

Missouri has 68,746 square miles of land, 24% more than Illinois's 55,513. The largest county-equivalent in Illinois is McLean County at 1,183 square miles; in Missouri it is Texas County at 1,177.

Counties

Missouri is divided into 115 county-equivalents and Illinois into 102, so an average Missouri county covers 598 square miles against 544. The typical county in Illinois has 24,447 residents, against 19,100 in Missouri. The most populous are Cook County (5,182,617) and St. Louis County (992,929).

41 county names appear on both sides of the border: Boone, Carroll, Cass, Christian, Clark, Clay, Clinton, Crawford, DeKalb, Douglas, Franklin, Greene, Grundy, Henry, Jackson, Jasper, Jefferson, Johnson, Knox, Lawrence, Livingston, Macon, Madison, Marion, Mercer, Monroe, Montgomery, Morgan, Perry, Pike, Pulaski, Putnam, Randolph, Saline, Schuyler, Scott, Shelby, St. Clair, Warren, Washington, Wayne. Use the FIPS code, not the name, when joining data across the two states.

Household income

The median county in Illinois has a household income of $65,901, 17% above Missouri's $56,121. The highest county incomes are Kendall County ($114,606) in Illinois and St. Charles County ($98,765) in Missouri, from SAIPE 2023.

Capitals and daylight

Springfield and Jefferson City are 159 miles apart in a straight line; from Springfield the initial bearing is 239°, WSW. On June 21, 2026, Springfield gets 15 h 00 min of daylight and Jefferson City 14 h 52 min; on December 21 the figures are 9 h 21 min and 9 h 28 min. Month by month tables are on the Springfield and Jefferson City daylight pages.

Where they sit

Both are in the Midwest region, but Illinois is in the East North Central division and Missouri in the West North Central division. By county internal points, Illinois spans 2 UTM zones and Missouri 2.