The map above shows Illinois and Pennsylvania side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Illinois vs Pennsylvania Geography
Land area: Illinois has a land area of 55,513 square miles (143,778 km²), while Pennsylvania has 44,742 square miles (115,882 km²). Illinois' land area is 1.2 times (24%) larger than Pennsylvania's.
Total area: Illinois: 57,913 square miles (149,995 km²) vs Pennsylvania: 46,054 square miles (119,279 km²), including inland and coastal water. Illinois' total area is 1.3 times (26%) larger than Pennsylvania's.
Length: Illinois is 390 miles (628 km) long from north to south; Pennsylvania is 284 miles (458 km). Illinois' north-south length is 1.4 times (37%) longer than Pennsylvania's.
Width: Illinois spans 283 miles (456 km) east to west; Pennsylvania spans 307 miles (495 km). Pennsylvania's east-west width is 1.1 times (8%) wider than Illinois'.
Highest point: Illinois's highest point is Charles Mound at 1,232 feet (376 m); Pennsylvania's is Mount Davis at 3,210 feet (978 m). Mount Davis is 1,978 feet higher than Charles Mound.
Lowest point: Illinois's lowest point is Mississippi River at 292 feet; Pennsylvania's is Delaware River at 0 feet. Pennsylvania's lowest point is 292 feet lower.
Illinois vs Pennsylvania Population and History
Population: Illinois has a population of 12,710,158 (2024), while Pennsylvania has 13,078,751 (2024). Illinois and Pennsylvania have about the same population.
Population density: Illinois: 229.0 people per square mile vs Pennsylvania: 292.3. Pennsylvania's population density is 1.3 times (28%) higher than Illinois'.
Biggest city: Illinois's biggest city is Chicago with 2,721,308 people; Pennsylvania's is Philadelphia with 1,573,916. Chicago's population is 1.7 times (73%) larger than Philadelphia's.
Largest metro area: Illinois's largest metropolitan area is Chicago-Naperville-Elgin, IL-IN metro area (9,408,576 people) vs Pennsylvania's Philadelphia-Camden-Wilmington, PA-NJ-DE-MD metro area (6,330,422). Chicago-Naperville-Elgin, IL-IN metro area's population is 1.5 times (49%) larger than Philadelphia-Camden-Wilmington, PA-NJ-DE-MD metro area's.
History: Illinois: Admitted to the Union on December 3, 1818, as the 21st state. Pennsylvania: Admitted to the Union on December 12, 1787, as the 2nd state. In its current form, Pennsylvania is the older of the two by 31 years.
Illinois vs Pennsylvania Economy
GDP: Illinois's GDP is $1,148.1 billion (2024) vs Pennsylvania's $1,007.9 billion. Illinois' economic output is 1.1 times (14%) larger than Pennsylvania's.
GDP per capita: Illinois: $90,330 per person vs Pennsylvania: $77,062. Illinois' GDP per capita is 1.2 times (17%) higher than Pennsylvania's.
Average income: Illinois: $74,522 vs Pennsylvania: $70,678 average income per person (per capita personal income). Illinois' average income is 1.1 times (5%) higher than Pennsylvania's.
Illinois vs Pennsylvania Counties
Number of counties: Illinois has 102 counties, while Pennsylvania has 67. Illinois' county count is 1.5 times (52%) higher than Pennsylvania's.
Biggest county by area: Illinois's largest county is McLean County at 1,183 square miles; Pennsylvania's is Lycoming County at 1,229 square miles. McLean County and Lycoming County have about the same land area.
Smallest county by area: Illinois: Putnam County (160 sq mi) vs Pennsylvania: Montour County (130 sq mi). Putnam County's land area is 1.2 times (23%) larger than Montour County's.
Most populous county: Illinois: Cook County (5,182,617 people) vs Pennsylvania: Philadelphia County (1,573,916 people). Cook County's population is 3.3 times (229%) larger than Philadelphia County's.
Least populous county: Illinois: Hardin County (3,550 people) vs Pennsylvania: Cameron County (4,348 people). Cameron County's population is 1.2 times (22%) larger than Hardin County's.
Richest county: Illinois: Cumberland County ($104,890 per capita income) vs Pennsylvania: Chester County ($110,883). Chester County's income is 1.1 times (6%) richer than Cumberland County's.
Poorest county: Illinois: Lawrence County ($43,606 per capita income) vs Pennsylvania: Forest County ($30,234). Lawrence County's income is 1.4 times (44%) richer than Forest County's.
Illinois vs Pennsylvania Taxes
State income tax: Illinois has a top income tax rate of 4.95%, while Pennsylvania has a top income tax rate of 3.07%. Illinois's top rate is 1.88 percentage points higher.
Property tax: Illinois: 1.92% effective rate vs Pennsylvania: 1.16% of home value per year. Illinois's rate is 0.76 percentage points higher.
Sales tax: Illinois: 8.98% combined state and average local rate vs Pennsylvania: 6.34%. Illinois's combined rate is 2.64 percentage points higher.
Official Websites
Illinois official website · Pennsylvania official website
More Size Comparisons
All Illinois size comparisons · All Pennsylvania 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.