The map above shows Illinois and South Dakota side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Illinois vs South Dakota Geography
Land area
- Illinois has a land area of 55,513 square miles (143,778 km²), while South Dakota has 75,808 square miles (196,342 km²).
- South Dakota's land area is 1.4 times (37%) larger than Illinois'.
Total area
- Illinois: 57,913 square miles (149,995 km²) vs South Dakota: 77,116 square miles (199,729 km²), including inland and coastal water.
- South Dakota's total area is 1.3 times (33%) larger than Illinois'.
Length
- Illinois is 390 miles (628 km) long from north to south; South Dakota is 443 miles (712 km).
- South Dakota's north-south length is 1.1 times (14%) longer than Illinois'.
Width
- Illinois spans 283 miles (456 km) east to west; South Dakota spans 371 miles (597 km).
- South Dakota's east-west width is 1.3 times (31%) wider than Illinois'.
Highest point
- Illinois's highest point is Charles Mound at 1,232 feet (376 m); South Dakota's is Black Elk Peak at 7,198 feet (2,194 m).
- Black Elk Peak is 5,966 feet higher than Charles Mound.
Lowest point
- Illinois's lowest point is Mississippi River at 292 feet; South Dakota's is Big Stone Lake at 966 feet.
- Illinois's lowest point is 674 feet lower.
Illinois vs South Dakota Population and History
Population
- Illinois has a population of 12,710,158 (2024), while South Dakota has 924,669 (2024).
- Illinois' population is 13.7 times larger than South Dakota's.
Population density
- Illinois: 229.0 people per square mile vs South Dakota: 12.2.
- Illinois' population density is 18.8 times higher than South Dakota's.
Biggest city
- Illinois's biggest city is Chicago with 2,721,308 people; South Dakota's is Sioux Falls with 209,289.
- Chicago's population is 13.0 times larger than Sioux Falls'.
Largest metro area
- Illinois's largest metropolitan area is Chicago-Naperville-Elgin, IL-IN metro area (9,408,576 people) vs South Dakota's Sioux Falls, SD-MN metro area (308,266).
- Chicago-Naperville-Elgin, IL-IN metro area's population is 30.5 times larger than Sioux Falls, SD-MN metro area's.
History
- Illinois: Admitted to the Union on December 3, 1818, as the 21st state.
- South Dakota: Admitted to the Union on November 2, 1889, as the 40th state.
- In its current form, Illinois is the older of the two by 71 years.
Illinois vs South Dakota Economy
GDP
- Illinois's GDP is $1,148.1 billion (2024) vs South Dakota's $76.8 billion.
- Illinois' economic output is 14.9 times larger than South Dakota's.
GDP per capita
- Illinois: $90,330 per person vs South Dakota: $83,052.
- Illinois' GDP per capita is 1.1 times (9%) higher than South Dakota's.
Average income
- Illinois: $74,522 vs South Dakota: $75,699 average income per person (per capita personal income).
- Illinois and South Dakota have about the same average income.
Illinois vs South Dakota Counties
Number of counties
- Illinois has 102 counties, while South Dakota has 66.
- Illinois' county count is 1.5 times (55%) higher than South Dakota's.
Biggest county by area
- Illinois's largest county is McLean County at 1,183 square miles; South Dakota's is Meade County at 3,471 square miles.
- Meade County's land area is 2.9 times (193%) larger than McLean County's.
Smallest county by area
- Illinois: Putnam County (160 sq mi) vs South Dakota: Clay County (412 sq mi).
- Clay County's land area is 2.6 times (157%) larger than Putnam County's.
Most populous county
- Illinois: Cook County (5,182,617 people) vs South Dakota: Minnehaha County (208,639 people).
- Cook County's population is 24.8 times larger than Minnehaha County's.
Least populous county
- Illinois: Hardin County (3,550 people) vs South Dakota: Jones County (874 people).
- Hardin County's population is 4.1 times (306%) larger than Jones County's.
Richest county
- Illinois: Cumberland County ($104,890 per capita income) vs South Dakota: Union County ($146,712).
- Union County's income is 1.4 times (40%) richer than Cumberland County's.
Poorest county
- Illinois: Lawrence County ($43,606 per capita income) vs South Dakota: Ziebach County ($32,778).
- Lawrence County's income is 1.3 times (33%) richer than Ziebach County's.
Illinois vs South Dakota Taxes
State income tax
- Illinois has a top income tax rate of 4.95%, while South Dakota has no state income tax.
- Illinois's top rate is 4.95 percentage points higher.
Property tax
- Illinois: 1.92% effective rate vs South Dakota: 1.02% of home value per year.
- Illinois's rate is 0.9 percentage points higher.
Sales tax
- Illinois: 8.98% combined state and average local rate vs South Dakota: 6.11%.
- Illinois's combined rate is 2.87 percentage points higher.
Official Websites
Illinois official website · South Dakota official website
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More Size Comparisons
All Illinois size comparisons · All South Dakota 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.