Illinois vs Kentucky

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, 2.8 times Kentucky's 4,588,372. Illinois ranks 6th and Kentucky 26th of the 50 states and DC. Illinois is the more crowded, with 229.0 people per square mile against 116.2, 97% more.

Land area

Illinois has 55,513 square miles of land, 41% more than Kentucky's 39,485. The largest county-equivalent in Illinois is McLean County at 1,183 square miles; in Kentucky it is Pike County at 786.

Counties

Kentucky is divided into 120 county-equivalents and Illinois into 102, so an average Kentucky county covers 329 square miles against 544. The typical county in Illinois has 24,447 residents, against 19,740 in Kentucky. The most populous are Cook County (5,182,617) and Jefferson County (793,881).

42 county names appear on both sides of the border: Boone, Carroll, Christian, Clark, Clay, Clinton, Cumberland, Fayette, Franklin, Fulton, Gallatin, Hancock, Hardin, Henderson, Henry, Jackson, Jefferson, Johnson, Knox, Lawrence, Lee, Livingston, Logan, Madison, Marion, Marshall, Mason, McLean, Mercer, Monroe, Montgomery, Morgan, Perry, Pike, Pulaski, Scott, Shelby, Union, Warren, Washington, Wayne, Woodford. 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, 19% above Kentucky's $55,510. The highest county incomes are Kendall County ($114,606) in Illinois and Oldham County ($120,818) in Kentucky, from SAIPE 2023.

Capitals and daylight

Springfield and Frankfort are 279 miles apart in a straight line; from Springfield the initial bearing is 112°, ESE. On June 21, 2026, Springfield gets 15 h 00 min of daylight and Frankfort 14 h 49 min; on December 21 the figures are 9 h 21 min and 9 h 30 min. Month by month tables are on the Springfield and Frankfort daylight pages.

Where they sit

The border between them is also a Census region boundary: Illinois is in the Midwest and Kentucky in the South. By county internal points, Illinois spans 2 UTM zones and Kentucky 2.