The map above shows Idaho and South Dakota side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Idaho vs South Dakota Geography
Land area
- Idaho has a land area of 82,645 square miles (214,051 km²), while South Dakota has 75,808 square miles (196,342 km²).
- Idaho's land area is 1.1 times (9%) larger than South Dakota's.
Total area
- Idaho: 83,569 square miles (216,441 km²) vs South Dakota: 77,116 square miles (199,729 km²), including inland and coastal water.
- Idaho's total area is 1.1 times (8%) larger than South Dakota's.
Length
- Idaho is 483 miles (778 km) long from north to south; South Dakota is 443 miles (712 km).
- Idaho's north-south length is 1.1 times (9%) longer than South Dakota's.
Width
- Idaho spans 352 miles (566 km) east to west; South Dakota spans 371 miles (597 km).
- South Dakota's east-west width is 1.1 times (5%) wider than Idaho's.
Highest point
- Idaho's highest point is Borah Peak at 12,631 feet (3,850 m); South Dakota's is Black Elk Peak at 7,198 feet (2,194 m).
- Borah Peak is 5,433 feet higher than Black Elk Peak.
Lowest point
- Idaho's lowest point is Snake River at 718 feet; South Dakota's is Big Stone Lake at 966 feet.
- Idaho's lowest point is 248 feet lower.
Idaho vs South Dakota Population and History
Population
- Idaho has a population of 2,001,619 (2024), while South Dakota has 924,669 (2024).
- Idaho's population is 2.2 times (116%) larger than South Dakota's.
Population density
- Idaho: 24.2 people per square mile vs South Dakota: 12.2.
- Idaho's population density is 2.0 times (98%) higher than South Dakota's.
Biggest city
- Idaho's biggest city is Boise with 237,963 people; South Dakota's is Sioux Falls with 209,289.
- Boise's population is 1.1 times (14%) larger than Sioux Falls'.
Largest metro area
- Idaho's largest metropolitan area is Boise City, ID metro area (845,877 people) vs South Dakota's Sioux Falls, SD-MN metro area (308,266).
- Boise City, ID metro area's population is 2.7 times (174%) larger than Sioux Falls, SD-MN metro area's.
History
- Idaho: Admitted to the Union on July 3, 1890, as the 43rd state.
- South Dakota: Admitted to the Union on November 2, 1889, as the 40th state.
- In its current form, South Dakota is the older of the two by 1 years.
Idaho vs South Dakota Economy
GDP
- Idaho's GDP is $129.0 billion (2024) vs South Dakota's $76.8 billion.
- Idaho's economic output is 1.7 times (68%) larger than South Dakota's.
GDP per capita
- Idaho: $64,457 per person vs South Dakota: $83,052.
- South Dakota's GDP per capita is 1.3 times (29%) higher than Idaho's.
Average income
- Idaho: $62,323 vs South Dakota: $75,699 average income per person (per capita personal income).
- South Dakota's average income is 1.2 times (21%) higher than Idaho's.
Idaho vs South Dakota Counties
Number of counties
- Idaho has 44 counties, while South Dakota has 66.
- South Dakota's county count is 1.5 times (50%) higher than Idaho's.
Biggest county by area
- Idaho's largest county is Idaho County at 8,478 square miles; South Dakota's is Meade County at 3,471 square miles.
- Idaho County's land area is 2.4 times (144%) larger than Meade County's.
Smallest county by area
- Idaho: Payette County (407 sq mi) vs South Dakota: Clay County (412 sq mi).
- Payette County and Clay County have about the same land area.
Most populous county
- Idaho: Ada County (535,799 people) vs South Dakota: Minnehaha County (208,639 people).
- Ada County's population is 2.6 times (157%) larger than Minnehaha County's.
Least populous county
- Idaho: Clark County (794 people) vs South Dakota: Jones County (874 people).
- Jones County's population is 1.1 times (10%) larger than Clark County's.
Richest county
- Idaho: Blaine County ($202,612 per capita income) vs South Dakota: Union County ($146,712).
- Blaine County's income is 1.4 times (38%) richer than Union County's.
Poorest county
- Idaho: Madison County ($29,485 per capita income) vs South Dakota: Ziebach County ($32,778).
- Ziebach County's income is 1.1 times (11%) richer than Madison County's.
Idaho vs South Dakota Taxes
State income tax
- Idaho has a top income tax rate of 5.3%, while South Dakota has no state income tax.
- Idaho's top rate is 5.3 percentage points higher.
Property tax
- Idaho: 0.43% effective rate vs South Dakota: 1.02% of home value per year.
- South Dakota's rate is 0.59 percentage points higher.
Sales tax
- Idaho: 6.03% combined state and average local rate vs South Dakota: 6.11%.
- South Dakota's combined rate is 0.08 percentage points higher.
Official Websites
Idaho official website · South Dakota official website
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More Size Comparisons
All Idaho 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.