The map above shows Illinois and Montana side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Illinois vs Montana Geography
Land area
- Illinois has a land area of 55,513 square miles (143,778 km²), while Montana has 145,550 square miles (376,973 km²).
- Montana's land area is 2.6 times (162%) larger than Illinois'.
Total area
- Illinois: 57,913 square miles (149,995 km²) vs Montana: 147,043 square miles (380,840 km²), including inland and coastal water.
- Montana's total area is 2.5 times (154%) larger than Illinois'.
Length
- Illinois is 390 miles (628 km) long from north to south; Montana is 319 miles (514 km).
- Illinois' north-south length is 1.2 times (22%) longer than Montana's.
Width
- Illinois spans 283 miles (456 km) east to west; Montana spans 607 miles (976 km).
- Montana's east-west width is 2.1 times (114%) wider than Illinois'.
Highest point
- Illinois's highest point is Charles Mound at 1,232 feet (376 m); Montana's is Granite Peak at 12,767 feet (3,891 m).
- Granite Peak is 11,535 feet higher than Charles Mound.
Lowest point
- Illinois's lowest point is Mississippi River at 292 feet; Montana's is Kootenai River at 1,805 feet.
- Illinois's lowest point is 1,513 feet lower.
Illinois vs Montana Population and History
Population
- Illinois has a population of 12,710,158 (2024), while Montana has 1,137,233 (2024).
- Illinois' population is 11.2 times larger than Montana's.
Population density
- Illinois: 229.0 people per square mile vs Montana: 7.8.
- Illinois' population density is 29.4 times higher than Montana's.
Biggest city
- Illinois's biggest city is Chicago with 2,721,308 people; Montana's is Billings with 121,483.
- Chicago's population is 22.4 times larger than Billings'.
Largest metro area
- Illinois's largest metropolitan area is Chicago-Naperville-Elgin, IL-IN metro area (9,408,576 people) vs Montana's Billings, MT metro area (192,531).
- Chicago-Naperville-Elgin, IL-IN metro area's population is 48.9 times larger than Billings, MT metro area's.
History
- Illinois: Admitted to the Union on December 3, 1818, as the 21st state.
- Montana: Admitted to the Union on November 8, 1889, as the 41st state.
- In its current form, Illinois is the older of the two by 71 years.
Illinois vs Montana Economy
GDP
- Illinois's GDP is $1,148.1 billion (2024) vs Montana's $78.4 billion.
- Illinois' economic output is 14.6 times larger than Montana's.
GDP per capita
- Illinois: $90,330 per person vs Montana: $68,975.
- Illinois' GDP per capita is 1.3 times (31%) higher than Montana's.
Average income
- Illinois: $74,522 vs Montana: $69,240 average income per person (per capita personal income).
- Illinois' average income is 1.1 times (8%) higher than Montana's.
Illinois vs Montana Counties
Number of counties
- Illinois has 102 counties, while Montana has 56.
- Illinois' county count is 1.8 times (82%) higher than Montana's.
Biggest county by area
- Illinois's largest county is McLean County at 1,183 square miles; Montana's is Beaverhead County at 5,543 square miles.
- Beaverhead County's land area is 4.7 times (368%) larger than McLean County's.
Smallest county by area
- Illinois: Putnam County (160 sq mi) vs Montana: Silver Bow County (718 sq mi).
- Silver Bow County's land area is 4.5 times (348%) larger than Putnam County's.
Most populous county
- Illinois: Cook County (5,182,617 people) vs Montana: Yellowstone County (171,583 people).
- Cook County's population is 30.2 times larger than Yellowstone County's.
Least populous county
- Illinois: Hardin County (3,550 people) vs Montana: Petroleum County (525 people).
- Hardin County's population is 6.8 times (576%) larger than Petroleum County's.
Richest county
- Illinois: Cumberland County ($104,890 per capita income) vs Montana: Gallatin County ($94,573).
- Cumberland County's income is 1.1 times (11%) richer than Gallatin County's.
Poorest county
- Illinois: Lawrence County ($43,606 per capita income) vs Montana: Blaine County ($37,554).
- Lawrence County's income is 1.2 times (16%) richer than Blaine County's.
Illinois vs Montana Taxes
State income tax
- Illinois has a top income tax rate of 4.95%, while Montana has a top income tax rate of 5.65%.
- Montana's top rate is 0.7 percentage points higher.
Property tax
- Illinois: 1.92% effective rate vs Montana: 0.69% of home value per year.
- Illinois's rate is 1.23 percentage points higher.
Sales tax
- Illinois: 8.98% combined state and average local rate vs Montana: 0%.
- Illinois's combined rate is 8.98 percentage points higher.
Official Websites
Illinois official website · Montana official website
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More Size Comparisons
All Illinois size comparisons · All Montana 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.