The map above shows Montana and South Dakota side by side at exactly the same scale, using equal-area projections, so their true relative sizes are preserved.
Montana vs South Dakota Geography
Land area: Montana has a land area of 145,550 square miles (376,973 km²), while South Dakota has 75,808 square miles (196,342 km²). Montana's land area is 1.9 times (92%) larger than South Dakota's.
Total area: Montana: 147,043 square miles (380,840 km²) vs South Dakota: 77,116 square miles (199,729 km²), including inland and coastal water. Montana's total area is 1.9 times (91%) larger than South Dakota's.
Length: Montana is 319 miles (514 km) long from north to south; South Dakota is 443 miles (712 km). South Dakota's north-south length is 1.4 times (39%) longer than Montana's.
Width: Montana spans 607 miles (976 km) east to west; South Dakota spans 371 miles (597 km). Montana's east-west width is 1.6 times (64%) wider than South Dakota's.
Highest point: Montana's highest point is Granite Peak at 12,767 feet (3,891 m); South Dakota's is Black Elk Peak at 7,198 feet (2,194 m). Granite Peak is 5,569 feet higher than Black Elk Peak.
Lowest point: Montana's lowest point is Kootenai River at 1,805 feet; South Dakota's is Big Stone Lake at 966 feet. South Dakota's lowest point is 839 feet lower.
Montana vs South Dakota Population and History
Population: Montana has a population of 1,137,233 (2024), while South Dakota has 924,669 (2024). Montana's population is 1.2 times (23%) larger than South Dakota's.
Population density: Montana: 7.8 people per square mile vs South Dakota: 12.2. South Dakota's population density is 1.6 times (56%) higher than Montana's.
Biggest city: Montana's biggest city is Billings with 121,483 people; South Dakota's is Sioux Falls with 209,289. Sioux Falls' population is 1.7 times (72%) larger than Billings'.
Largest metro area: Montana's largest metropolitan area is Billings, MT metro area (192,531 people) vs South Dakota's Sioux Falls, SD-MN metro area (308,266). Sioux Falls, SD-MN metro area's population is 1.6 times (60%) larger than Billings, MT metro area's.
History: Montana: Admitted to the Union on November 8, 1889, as the 41st state. South Dakota: Admitted to the Union on November 2, 1889, as the 40th state.
Montana vs South Dakota Economy
GDP: Montana's GDP is $78.4 billion (2024) vs South Dakota's $76.8 billion. Montana and South Dakota have about the same economic output.
GDP per capita: Montana: $68,975 per person vs South Dakota: $83,052. South Dakota's GDP per capita is 1.2 times (20%) higher than Montana's.
Average income: Montana: $69,240 vs South Dakota: $75,699 average income per person (per capita personal income). South Dakota's average income is 1.1 times (9%) higher than Montana's.
Montana vs South Dakota Counties
Number of counties: Montana has 56 counties, while South Dakota has 66. South Dakota's county count is 1.2 times (18%) higher than Montana's.
Biggest county by area: Montana's largest county is Beaverhead County at 5,543 square miles; South Dakota's is Meade County at 3,471 square miles. Beaverhead County's land area is 1.6 times (60%) larger than Meade County's.
Smallest county by area: Montana: Silver Bow County (718 sq mi) vs South Dakota: Clay County (412 sq mi). Silver Bow County's land area is 1.7 times (74%) larger than Clay County's.
Most populous county: Montana: Yellowstone County (171,583 people) vs South Dakota: Minnehaha County (208,639 people). Minnehaha County's population is 1.2 times (22%) larger than Yellowstone County's.
Least populous county: Montana: Petroleum County (525 people) vs South Dakota: Jones County (874 people). Jones County's population is 1.7 times (66%) larger than Petroleum County's.
Richest county: Montana: Gallatin County ($94,573 per capita income) vs South Dakota: Union County ($146,712). Union County's income is 1.6 times (55%) richer than Gallatin County's.
Poorest county: Montana: Blaine County ($37,554 per capita income) vs South Dakota: Ziebach County ($32,778). Blaine County's income is 1.1 times (15%) richer than Ziebach County's.
Montana vs South Dakota Taxes
State income tax: Montana has a top income tax rate of 5.65%, while South Dakota has no state income tax. Montana's top rate is 5.65 percentage points higher.
Property tax: Montana: 0.69% effective rate vs South Dakota: 1.02% of home value per year. South Dakota's rate is 0.33 percentage points higher.
Sales tax: Montana: 0% combined state and average local rate vs South Dakota: 6.11%. South Dakota's combined rate is 6.11 percentage points higher.
Official Websites
Montana official website · South Dakota official website
More Size Comparisons
All Montana 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.