The map above shows Illinois and Washington side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Illinois vs Washington Geography
Land area: Illinois has a land area of 55,513 square miles (143,778 km²), while Washington has 66,455 square miles (172,119 km²). Washington's land area is 1.2 times (20%) larger than Illinois'.
Total area: Illinois: 57,913 square miles (149,995 km²) vs Washington: 71,301 square miles (184,668 km²), including inland and coastal water. Washington's total area is 1.2 times (23%) larger than Illinois'.
Length: Illinois is 390 miles (628 km) long from north to south; Washington is 238 miles (383 km). Illinois' north-south length is 1.6 times (64%) longer than Washington's.
Width: Illinois spans 283 miles (456 km) east to west; Washington spans 399 miles (641 km). Washington's east-west width is 1.4 times (41%) wider than Illinois'.
Highest point: Illinois's highest point is Charles Mound at 1,232 feet (376 m); Washington's is Mount Rainier at 14,409 feet (4,392 m). Mount Rainier is 13,177 feet higher than Charles Mound.
Lowest point: Illinois's lowest point is Mississippi River at 292 feet; Washington's is Pacific Ocean at 0 feet. Washington's lowest point is 292 feet lower.
Illinois vs Washington Population and History
Population: Illinois has a population of 12,710,158 (2024), while Washington has 7,958,180 (2024). Illinois' population is 1.6 times (60%) larger than Washington's.
Population density: Illinois: 229.0 people per square mile vs Washington: 119.8. Illinois' population density is 1.9 times (91%) higher than Washington's.
Biggest city: Illinois's biggest city is Chicago with 2,721,308 people; Washington's is Seattle with 780,995. Chicago's population is 3.5 times (248%) larger than Seattle's.
Largest metro area: Illinois's largest metropolitan area is Chicago-Naperville-Elgin, IL-IN metro area (9,408,576 people) vs Washington's Seattle-Tacoma-Bellevue, WA metro area (4,145,494). Chicago-Naperville-Elgin, IL-IN metro area's population is 2.3 times (127%) larger than Seattle-Tacoma-Bellevue, WA metro area's.
History: Illinois: Admitted to the Union on December 3, 1818, as the 21st state. Washington: Admitted to the Union on November 11, 1889, as the 42nd state. In its current form, Illinois is the older of the two by 71 years.
Illinois vs Washington Economy
GDP: Illinois's GDP is $1,148.1 billion (2024) vs Washington's $856.0 billion. Illinois' economic output is 1.3 times (34%) larger than Washington's.
GDP per capita: Illinois: $90,330 per person vs Washington: $107,564. Washington's GDP per capita is 1.2 times (19%) higher than Illinois'.
Average income: Illinois: $74,522 vs Washington: $85,187 average income per person (per capita personal income). Washington's average income is 1.1 times (14%) higher than Illinois'.
Illinois vs Washington Counties
Number of counties: Illinois has 102 counties, while Washington has 39. Illinois' county count is 2.6 times (162%) higher than Washington's.
Biggest county by area: Illinois's largest county is McLean County at 1,183 square miles; Washington's is Okanogan County at 5,266 square miles. Okanogan County's land area is 4.5 times (345%) larger than McLean County's.
Smallest county by area: Illinois: Putnam County (160 sq mi) vs Washington: San Juan County (174 sq mi). San Juan County's land area is 1.1 times (9%) larger than Putnam County's.
Most populous county: Illinois: Cook County (5,182,617 people) vs Washington: King County (2,340,211 people). Cook County's population is 2.2 times (121%) larger than King County's.
Least populous county: Illinois: Hardin County (3,550 people) vs Washington: Garfield County (2,404 people). Hardin County's population is 1.5 times (48%) larger than Garfield County's.
Richest county: Illinois: Cumberland County ($104,890 per capita income) vs Washington: King County ($128,684). King County's income is 1.2 times (23%) richer than Cumberland County's.
Poorest county: Illinois: Lawrence County ($43,606 per capita income) vs Washington: Ferry County ($50,456). Ferry County's income is 1.2 times (16%) richer than Lawrence County's.
Illinois vs Washington Taxes
State income tax: Illinois has a top income tax rate of 4.95%, while Washington has a 9% tax on capital gains only.
Property tax: Illinois: 1.92% effective rate vs Washington: 0.79% of home value per year. Illinois's rate is 1.13 percentage points higher.
Sales tax: Illinois: 8.98% combined state and average local rate vs Washington: 9.57%. Washington's combined rate is 0.59 percentage points higher.
Official Websites
Illinois official website · Washington official website
More Size Comparisons
All Illinois size comparisons · All Washington 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.