The map above shows Connecticut and Illinois side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Connecticut vs Illinois Geography
Land area
- Connecticut has a land area of 4,843 square miles (12,542 km²), while Illinois has 55,513 square miles (143,778 km²).
- Illinois' land area is 11.5 times larger than Connecticut's.
Total area
- Connecticut: 5,544 square miles (14,358 km²) vs Illinois: 57,913 square miles (149,995 km²), including inland and coastal water.
- Illinois' total area is 10.4 times larger than Connecticut's.
Length
- Connecticut is 73 miles (118 km) long from north to south; Illinois is 390 miles (628 km).
- Illinois' north-south length is 5.3 times (434%) longer than Connecticut's.
Width
- Connecticut spans 104 miles (167 km) east to west; Illinois spans 283 miles (456 km).
- Illinois' east-west width is 2.7 times (172%) wider than Connecticut's.
Highest point
- Connecticut's highest point is Mount Frissell (south slope) at 2,376 feet (724 m); Illinois's is Charles Mound at 1,232 feet (376 m).
- Mount Frissell (south slope) is 1,144 feet higher than Charles Mound.
Lowest point
- Connecticut's lowest point is Long Island Sound at 0 feet; Illinois's is Mississippi River at 292 feet.
- Connecticut's lowest point is 292 feet lower.
Connecticut vs Illinois Population and History
Population
- Connecticut has a population of 3,675,069 (2024), while Illinois has 12,710,158 (2024).
- Illinois' population is 3.5 times (246%) larger than Connecticut's.
Population density
- Connecticut: 758.9 people per square mile vs Illinois: 229.0.
- Connecticut's population density is 3.3 times (231%) higher than Illinois'.
Biggest city
- Connecticut's biggest city is Bridgeport with 151,599 people; Illinois's is Chicago with 2,721,308.
- Chicago's population is 18.0 times larger than Bridgeport's.
Largest metro area
- Connecticut's largest metropolitan area is Hartford-West Hartford-East Hartford, CT metro area (1,169,048 people) vs Illinois's Chicago-Naperville-Elgin, IL-IN metro area (9,408,576).
- Chicago-Naperville-Elgin, IL-IN metro area's population is 8.0 times (705%) larger than Hartford-West Hartford-East Hartford, CT metro area's.
History
- Connecticut: Admitted to the Union on January 9, 1788, as the 5th state.
- Illinois: Admitted to the Union on December 3, 1818, as the 21st state.
- In its current form, Connecticut is the older of the two by 30 years.
Connecticut vs Illinois Economy
GDP
- Connecticut's GDP is $356.8 billion (2024) vs Illinois's $1,148.1 billion.
- Illinois' economic output is 3.2 times (222%) larger than Connecticut's.
GDP per capita
- Connecticut: $97,096 per person vs Illinois: $90,330.
- Connecticut's GDP per capita is 1.1 times (7%) higher than Illinois'.
Average income
- Connecticut: $95,067 vs Illinois: $74,522 average income per person (per capita personal income).
- Connecticut's average income is 1.3 times (28%) higher than Illinois'.
Connecticut vs Illinois Counties
Number of counties
- Connecticut has 9 counties, while Illinois has 102.
- Illinois' county count is 11.3 times higher than Connecticut's.
Biggest county by area
- Connecticut's largest county is Capitol Planning Region at 1,027 square miles; Illinois's is McLean County at 1,183 square miles.
- McLean County's land area is 1.2 times (15%) larger than Capitol Planning Region's.
Smallest county by area
- Connecticut: Greater Bridgeport Planning Region (140 sq mi) vs Illinois: Putnam County (160 sq mi).
- Putnam County's land area is 1.1 times (14%) larger than Greater Bridgeport Planning Region's.
Most populous county
- Connecticut: Capitol Planning Region (991,508 people) vs Illinois: Cook County (5,182,617 people).
- Cook County's population is 5.2 times (423%) larger than Capitol Planning Region's.
Least populous county
- Connecticut: Northeastern Connecticut Planning Region (97,701 people) vs Illinois: Hardin County (3,550 people).
- Northeastern Connecticut Planning Region's population is 27.5 times larger than Hardin County's.
Richest county
- Connecticut: Western Connecticut Planning Region ($165,513 per capita income) vs Illinois: Cumberland County ($104,890).
- Western Connecticut Planning Region's income is 1.6 times (58%) richer than Cumberland County's.
Poorest county
- Connecticut: Southeastern Connecticut Planning Region ($64,845 per capita income) vs Illinois: Lawrence County ($43,606).
- Southeastern Connecticut Planning Region's income is 1.5 times (49%) richer than Lawrence County's.
Connecticut vs Illinois Taxes
State income tax
- Connecticut has a top income tax rate of 6.99%, while Illinois has a top income tax rate of 4.95%.
- Connecticut's top rate is 2.04 percentage points higher.
Property tax
- Connecticut: 1.66% effective rate vs Illinois: 1.92% of home value per year.
- Illinois's rate is 0.26 percentage points higher.
Sales tax
- Connecticut: 6.35% combined state and average local rate vs Illinois: 8.98%.
- Illinois's combined rate is 2.63 percentage points higher.
Official Websites
Connecticut official website · Illinois official website
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More Size Comparisons
All Connecticut size comparisons · All Illinois 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.