Lake County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 11,059. Its county seat is Madison. The county was formed in 1873.

Geography

The terrain of Lake County consists of rolling hills, with the area devoted to agriculture. A tributary of the East Fork Vermillion River flows south-southeastward through the lower western part of the county, and Buffalo Creek flows southeastward from the central part of the county, leaving the county near its southeast corner. The terrain generally slopes to the south, although high points (ca. 1,814' ASL) are found on the north and south boundary lines and points between.

Lake County has a total area of 575 square miles (1,490 km), of which 563 square miles (1,460 km) is land and 12 square miles (31 km) (2.1%) is water.

Lakes

Protected areas

• Lake Herman State Park
• Walker's Point State Recreation Area

Major highways

• U.S. Highway 81
• South Dakota Highway 19
• South Dakota Highway 34

Adjacent counties

Demographics

Historical population

Census	Pop.	Note	%±
1880	2,657		—
1890	7,508		182.6%
1900	9,137		21.7%
1910	10,711		17.2%
1920	12,257		14.4%
1930	12,379		1.0%
1940	12,412		0.3%
1950	11,792		−5.0%
1960	11,764		−0.2%
1970	11,456		−2.6%
1980	10,724		−6.4%
1990	10,550		−1.6%
2000	11,276		6.9%
2010	11,200		−0.7%
2020	11,059		−1.3%
2023 (est.)	11,031		−0.3%
U.S. Decennial Census 1790-1960 1900-1990 1990-2000 2010-2020

2020 census

As of the 2020 census, there were 11,059 people, 4,576 households, and 2,804 families residing in the county. The population density was 19.6 inhabitants per square mile (7.6/km). There were 5,658 housing units.

2010 census

As of the 2010 census, there were 11,200 people, 4,483 households, and 2,814 families in the county. The population density was 19.9 inhabitants per square mile (7.7/km). There were 5,559 housing units at an average density of 9.9 units per square mile (3.8 units/km). The racial makeup of the county was 96.2% white, 0.7% Asian, 0.7% American Indian, 0.5% black or African American, 0.8% from other races, and 1.1% from two or more races. Those of Hispanic or Latino origin made up 1.6% of the population. In terms of ancestry, 50.7% were German, 20.6% were Norwegian, 12.4% were Irish, 6.6% were English, 6.2% were Dutch, 5.0% were Danish, and 5.0% were American.

Of the 4,483 households, 26.7% had children under the age of 18 living with them, 53.0% were married couples living together, 6.8% had a female householder with no husband present, 37.2% were non-families, and 30.9% of all households were made up of individuals. The average household size was 2.30 and the average family size was 2.88. The median age was 39.9 years.

The median income for a household in the county was $45,606 and the median income for a family was $57,753. Males had a median income of $36,370 versus $25,898 for females. The per capita income for the county was $22,447. About 6.5% of families and 12.1% of the population were below the poverty line, including 12.8% of those under age 18 and 8.8% of those age 65 or over.

Communities

City

• Madison (county seat)

Towns

• Brant Lake
• Nunda
• Ramona

Village

• Wentworth

Census-designated places

• Brant Lake South
• Chester
• Graceville Colony
• Lake Madison
• Rustic Acres Colony
• Winfred

Other unincorporated communities

• Franklin
• Junius
• Rutland

Townships

Historical townsite

• Saranac

Politics

Lake County voters have voted for Republican Party candidates in 62 percent of national elections since 1964.

United States presidential election results for Lake County, South Dakota

Year	Republican		Democratic		Third party
	No.	%	No.	%	No.	%
2020	3,681	62.68%	2,068	35.21%	124	2.11%
2016	4,038	59.50%	2,314	34.10%	434	6.40%
2012	3,419	54.40%	2,724	43.34%	142	2.26%
2008	2,993	48.61%	3,033	49.26%	131	2.13%
2004	3,359	55.92%	2,509	41.77%	139	2.31%
2000	2,724	52.85%	2,331	45.23%	99	1.92%
1996	1,966	38.41%	2,526	49.36%	626	12.23%
1992	1,890	33.81%	2,388	42.72%	1,312	23.47%
1988	2,439	47.62%	2,663	51.99%	20	0.39%
1984	3,027	55.92%	2,367	43.73%	19	0.35%
1980	3,093	52.85%	2,207	37.71%	552	9.43%
1976	2,530	46.20%	2,930	53.51%	16	0.29%
1972	2,919	50.14%	2,886	49.57%	17	0.29%
1968	2,876	53.68%	2,294	42.81%	188	3.51%
1964	2,417	44.72%	2,988	55.28%	0	0.00%
1960	3,520	61.28%	2,224	38.72%	0	0.00%
1956	3,404	62.32%	2,058	37.68%	0	0.00%
1952	4,020	73.28%	1,466	26.72%	0	0.00%
1948	2,837	56.95%	2,093	42.01%	52	1.04%
1944	2,956	65.70%	1,543	34.30%	0	0.00%
1940	4,179	68.87%	1,889	31.13%	0	0.00%
1936	3,182	52.95%	2,520	41.94%	307	5.11%
1932	2,222	41.09%	3,090	57.15%	95	1.76%
1928	3,048	63.41%	1,744	36.28%	15	0.31%
1924	1,888	45.35%	297	7.13%	1,978	47.51%
1920	2,333	69.98%	398	11.94%	603	18.09%
1916	1,398	55.04%	1,027	40.43%	115	4.53%
1912	0	0.00%	657	33.50%	1,304	66.50%
1908	1,415	65.60%	636	29.49%	106	4.91%
1904	1,728	78.90%	260	11.87%	202	9.22%
1900	1,172	55.57%	901	42.72%	36	1.71%
1896	864	46.10%	999	53.31%	11	0.59%
1892	742	43.47%	196	11.48%	769	45.05%

See also

• National Register of Historic Places listings in Lake County, South Dakota