Big Stone County is a county in the U.S. state of Minnesota. As of the 2020 census, the population was 5,166.^[2] Its county seat is Ortonville.^[3]

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Big Stone County
County
Big Stone County Courthouse in Ortonville, Minnesota.
Location within the U.S. state of Minnesota
Minnesota's location within the U.S.
Coordinates: 45°26′N 96°25′W
Country	United States
State	Minnesota
Founded	February 20, 1862 (created) 1874 (organized)[1]
Named for	Big Stone Lake
Seat	Ortonville
Largest city	Ortonville
Area
• Total	528 sq mi (1,370 km2)
• Land	499 sq mi (1,290 km2)
• Water	29 sq mi (80 km2)  5.5%
Population  (2020)
• Total	5,166
• Estimate  (2023)	5,105
• Density	10.1/sq mi (3.9/km2)
Time zone	UTC−6 (Central)
• Summer (DST)	UTC−5 (CDT)
Congressional district	7th
Website	www.bigstonecounty.org

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The county was formed in 1862, and was organized in 1874. It is named for Big Stone Lake.^[4][5]

Big Stone County lies on the western side of Minnesota. Its southwest boundary line abuts the east boundary line of the state of South Dakota. The Little Minnesota River flows along the county's southwestern boundary. Since 1937, a dam (Big Stone Lake Dam) has impounded the river's waters, creating Big Stone Lake. Water flowing out from this lake flows along the south boundary line of the county, and is known as the Minnesota River from that point. Fish Creek flows southwesterly through the northwestern part of the county, discharging into Big Stone Lake at the county's southwestern boundary.

The terrain of Big Stone County is low rolling hills, wooded or devoted to agriculture.^[6] The terrain generally slopes to the south and east, although its southwestern portion slopes to the river valley. Its highest point is on its north line near the northwestern corner, 2.9 miles (4.7 km) east of Lagoona Beach, at 1,201 ft (366 m) ASL.^[7][8] The county has a total area of 528 square miles (1,370 km²), of which 499 square miles (1,290 km²) is land and 29 square miles (75 km²) (5.5%) is water.^[9]

In recent years, average temperatures in the county seat of Ortonville have ranged from a low of 1 °F (−17 °C) in January to a high of 84 °F (29 °C) in July, although a record low of −44 °F (−42 °C) was recorded in February 1994 and a record high of 108 °F (42 °C) was recorded in July 1966. Average monthly precipitation ranged from 0.43 inches (11 mm) in December to 3.85 inches (98 mm) in July.^[12]

Between 1928 and 2008, Big Stone County voted Democrat in every election except for two nationwide Republican landslides in 1952 and 1980. The only other time between 1928 and 2000 that the Republican candidate lost by less than 10% was Ronald Reagan during his 1984 landslide reelection. Beginning in 2000, the Democrat margins began to shrink, with George W. Bush losing by about 2% in both 2000 and 2004, and by a margin of no more than 60 votes. Despite favoring Barack Obama by over 6% in 2008, this would prove to be the most recent time Big Stone County would vote Democrat. Mitt Romney narrowly carried the county by 40 votes and less than 1.5% in 2012. But in 2016, Donald Trump greatly expanded the thin margin Romney won the county by as Democratic candidate Hillary Clinton lost by nearly 25%, the first time a Republican won by more than 5% in the county since 1924. Trump further increased his margin of victory in 2020 to over 27%.

School districts include:^[26]

• Chokio-Alberta Public School District
• Clinton-Graceville-Beardsley School District
• Lac Qui Parle Valley School District
• Ortonville Public Schools

• National Register of Historic Places listings in Big Stone County, Minnesota
• List of Minnesota placenames of Native American origin