The map above shows Illinois and Kentucky side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Illinois vs Kentucky Geography
Land area: Illinois has a land area of 55,513 square miles (143,778 km²), while Kentucky has 39,485 square miles (102,267 km²). Illinois' land area is 1.4 times (41%) larger than Kentucky's.
Total area: Illinois: 57,913 square miles (149,995 km²) vs Kentucky: 40,406 square miles (104,651 km²), including inland and coastal water. Illinois' total area is 1.4 times (43%) larger than Kentucky's.
Length: Illinois is 390 miles (628 km) long from north to south; Kentucky is 257 miles (414 km). Illinois' north-south length is 1.5 times (52%) longer than Kentucky's.
Width: Illinois spans 283 miles (456 km) east to west; Kentucky spans 418 miles (672 km). Kentucky's east-west width is 1.5 times (48%) wider than Illinois'.
Highest point: Illinois's highest point is Charles Mound at 1,232 feet (376 m); Kentucky's is Black Mountain at 4,134 feet (1,260 m). Black Mountain is 2,902 feet higher than Charles Mound.
Lowest point: Illinois's lowest point is Mississippi River at 292 feet; Kentucky's is Mississippi River at 270 feet. Kentucky's lowest point is 22 feet lower.
Illinois vs Kentucky Population and History
Population: Illinois has a population of 12,710,158 (2024), while Kentucky has 4,588,372 (2024). Illinois' population is 2.8 times (177%) larger than Kentucky's.
Population density: Illinois: 229.0 people per square mile vs Kentucky: 116.2. Illinois' population density is 2.0 times (97%) higher than Kentucky's.
Biggest city: Illinois's biggest city is Chicago with 2,721,308 people; Kentucky's is Louisville with 640,796. Chicago's population is 4.2 times (325%) larger than Louisville's.
Largest metro area: Illinois's largest metropolitan area is Chicago-Naperville-Elgin, IL-IN metro area (9,408,576 people) vs Kentucky's Cincinnati, OH-KY-IN metro area (2,302,815). Chicago-Naperville-Elgin, IL-IN metro area's population is 4.1 times (309%) larger than Cincinnati, OH-KY-IN metro area's.
History: Illinois: Admitted to the Union on December 3, 1818, as the 21st state. Kentucky: Admitted to the Union on June 1, 1792, as the 15th state. In its current form, Kentucky is the older of the two by 26 years.
Illinois vs Kentucky Economy
GDP: Illinois's GDP is $1,148.1 billion (2024) vs Kentucky's $295.4 billion. Illinois' economic output is 3.9 times (289%) larger than Kentucky's.
GDP per capita: Illinois: $90,330 per person vs Kentucky: $64,375. Illinois' GDP per capita is 1.4 times (40%) higher than Kentucky's.
Average income: Illinois: $74,522 vs Kentucky: $58,256 average income per person (per capita personal income). Illinois' average income is 1.3 times (28%) higher than Kentucky's.
Illinois vs Kentucky Counties
Number of counties: Illinois has 102 counties, while Kentucky has 120. Kentucky's county count is 1.2 times (18%) higher than Illinois'.
Biggest county by area: Illinois's largest county is McLean County at 1,183 square miles; Kentucky's is Pike County at 786 square miles. McLean County's land area is 1.5 times (50%) larger than Pike County's.
Smallest county by area: Illinois: Putnam County (160 sq mi) vs Kentucky: Gallatin County (98 sq mi). Putnam County's land area is 1.6 times (63%) larger than Gallatin County's.
Most populous county: Illinois: Cook County (5,182,617 people) vs Kentucky: Jefferson County (793,881 people). Cook County's population is 6.5 times (553%) larger than Jefferson County's.
Least populous county: Illinois: Hardin County (3,550 people) vs Kentucky: Robertson County (2,382 people). Hardin County's population is 1.5 times (49%) larger than Robertson County's.
Richest county: Illinois: Cumberland County ($104,890 per capita income) vs Kentucky: Oldham County ($87,137). Cumberland County's income is 1.2 times (20%) richer than Oldham County's.
Poorest county: Illinois: Lawrence County ($43,606 per capita income) vs Kentucky: Elliott County ($31,817). Lawrence County's income is 1.4 times (37%) richer than Elliott County's.
Illinois vs Kentucky Taxes
State income tax: Illinois has a top income tax rate of 4.95%, while Kentucky has a top income tax rate of 3.5%. Illinois's top rate is 1.45 percentage points higher.
Property tax: Illinois: 1.92% effective rate vs Kentucky: 0.71% of home value per year. Illinois's rate is 1.21 percentage points higher.
Sales tax: Illinois: 8.98% combined state and average local rate vs Kentucky: 6%. Illinois's combined rate is 2.98 percentage points higher.
Official Websites
Illinois official website · Kentucky official website
More Size Comparisons
All Illinois size comparisons · All Kentucky size comparisons
Area, elevation and boundary figures come from official national statistics and US Census Bureau and Natural Earth boundary data; US state population, economic, county and tax figures come from the US Census Bureau, the Bureau of Economic Analysis and the Tax Foundation. Figures are rounded and for general reference.