The map above shows Idaho and Illinois side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Idaho vs Illinois Geography
Land area
- Idaho has a land area of 82,645 square miles (214,051 km²), while Illinois has 55,513 square miles (143,778 km²).
- Idaho's land area is 1.5 times (49%) larger than Illinois'.
Total area
- Idaho: 83,569 square miles (216,441 km²) vs Illinois: 57,913 square miles (149,995 km²), including inland and coastal water.
- Idaho's total area is 1.4 times (44%) larger than Illinois'.
Length
- Idaho is 483 miles (778 km) long from north to south; Illinois is 390 miles (628 km).
- Idaho's north-south length is 1.2 times (24%) longer than Illinois'.
Width
- Idaho spans 352 miles (566 km) east to west; Illinois spans 283 miles (456 km).
- Idaho's east-west width is 1.2 times (24%) wider than Illinois'.
Highest point
- Idaho's highest point is Borah Peak at 12,631 feet (3,850 m); Illinois's is Charles Mound at 1,232 feet (376 m).
- Borah Peak is 11,399 feet higher than Charles Mound.
Lowest point
- Idaho's lowest point is Snake River at 718 feet; Illinois's is Mississippi River at 292 feet.
- Illinois's lowest point is 426 feet lower.
Idaho vs Illinois Population and History
Population
- Idaho has a population of 2,001,619 (2024), while Illinois has 12,710,158 (2024).
- Illinois' population is 6.3 times (535%) larger than Idaho's.
Population density
- Idaho: 24.2 people per square mile vs Illinois: 229.0.
- Illinois' population density is 9.5 times (846%) higher than Idaho's.
Biggest city
- Idaho's biggest city is Boise with 237,963 people; Illinois's is Chicago with 2,721,308.
- Chicago's population is 11.4 times larger than Boise's.
Largest metro area
- Idaho's largest metropolitan area is Boise City, ID metro area (845,877 people) vs Illinois's Chicago-Naperville-Elgin, IL-IN metro area (9,408,576).
- Chicago-Naperville-Elgin, IL-IN metro area's population is 11.1 times larger than Boise City, ID metro area's.
History
- Idaho: Admitted to the Union on July 3, 1890, as the 43rd state.
- Illinois: Admitted to the Union on December 3, 1818, as the 21st state.
- In its current form, Illinois is the older of the two by 72 years.
Idaho vs Illinois Economy
GDP
- Idaho's GDP is $129.0 billion (2024) vs Illinois's $1,148.1 billion.
- Illinois' economic output is 8.9 times (790%) larger than Idaho's.
GDP per capita
- Idaho: $64,457 per person vs Illinois: $90,330.
- Illinois' GDP per capita is 1.4 times (40%) higher than Idaho's.
Average income
- Idaho: $62,323 vs Illinois: $74,522 average income per person (per capita personal income).
- Illinois' average income is 1.2 times (20%) higher than Idaho's.
Idaho vs Illinois Counties
Number of counties
- Idaho has 44 counties, while Illinois has 102.
- Illinois' county count is 2.3 times (132%) higher than Idaho's.
Biggest county by area
- Idaho's largest county is Idaho County at 8,478 square miles; Illinois's is McLean County at 1,183 square miles.
- Idaho County's land area is 7.2 times (616%) larger than McLean County's.
Smallest county by area
- Idaho: Payette County (407 sq mi) vs Illinois: Putnam County (160 sq mi).
- Payette County's land area is 2.5 times (154%) larger than Putnam County's.
Most populous county
- Idaho: Ada County (535,799 people) vs Illinois: Cook County (5,182,617 people).
- Cook County's population is 9.7 times (867%) larger than Ada County's.
Least populous county
- Idaho: Clark County (794 people) vs Illinois: Hardin County (3,550 people).
- Hardin County's population is 4.5 times (347%) larger than Clark County's.
Richest county
- Idaho: Blaine County ($202,612 per capita income) vs Illinois: Cumberland County ($104,890).
- Blaine County's income is 1.9 times (93%) richer than Cumberland County's.
Poorest county
- Idaho: Madison County ($29,485 per capita income) vs Illinois: Lawrence County ($43,606).
- Lawrence County's income is 1.5 times (48%) richer than Madison County's.
Idaho vs Illinois Taxes
State income tax
- Idaho has a top income tax rate of 5.3%, while Illinois has a top income tax rate of 4.95%.
- Idaho's top rate is 0.35 percentage points higher.
Property tax
- Idaho: 0.43% effective rate vs Illinois: 1.92% of home value per year.
- Illinois's rate is 1.49 percentage points higher.
Sales tax
- Idaho: 6.03% combined state and average local rate vs Illinois: 8.98%.
- Illinois's combined rate is 2.95 percentage points higher.
Official Websites
Idaho official website · Illinois official website
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More Size Comparisons
All Idaho 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.