| County: | Marshall County |
| State: | South Dakota |
| Founded Year: | 1885 |
| Seat Wl: | Britton |
| Largest City Wl: | Britton |
| Area Total Sq Mi: | 886 |
| Area Land Sq Mi: | 838 |
| Area Water Sq Mi: | 48 |
| Area Percentage: | 5.4 |
| Population As Of: | 2020 |
| Population Total: | 4306 |
| Pop Est As Of: | 2023 |
| Population Est: | 4390 |
| Population Density Sq Mi: | auto |
| Ex Image: | Marshall County, SD, courthouse from NW 1.jpg |
| Ex Image Cap: | Marshall County Courthouse in Britton |
| Time Zone: | Central |
| Web: | http://marshall.sdcounties.org/ |
| Named For: | Marshall Vincent |
| District: | At-large |
Marshall County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 4,306.[1] Its county seat is Britton.[2] The county was created on May 2, 1885,[3] and was named for Marshall Vincent, who homesteaded near Andover, South Dakota.[4]
Marshall County lies on the north side of South Dakota. Its north boundary line abuts the south boundary line of the state of North Dakota. Its terrain consists of rolling hills, with numerous lakes and ponds in the SE portion.[5] Its terrain slopes to the northeast, and its highest point is near its SE corner, at 2034feet ASL.[6]
Marshall County has a total area of, of which is land and (5.4%) is water.[7] The county is drained by the Crow Creek, a tributary of the James River, and the Wild Rice River, a tributary of the Red River of the North.[8] A portion of the Lake Traverse Indian Reservation is located in the eastern part of the county.
As of the 2020 census, there were 4,306 people, 1,702 households, and 1,131 families residing in the county.[9] The population density was . There were 2,394 housing units.
As of the 2010 census, there were 4,656 people, 1,815 households, and 1,154 families in the county. The population density was . There were 2,534 housing units at an average density of 3/mi2. The racial makeup of the county was 85.4% white, 7.6% American Indian, 0.2% black or African American, 0.2% Asian, 5.6% from other races, and 1.1% from two or more races. Those of Hispanic or Latino origin made up 6.8% of the population. In terms of ancestry, 45.6% were German, 30.6% were Norwegian, 6.8% were Swedish, 5.8% were Irish, 5.2% were English, and 2.7% were American.
Of the 1,815 households, 24.4% had children under the age of 18 living with them, 52.8% were married couples living together, 6.0% had a female householder with no husband present, 36.4% were non-families, and 31.4% of all households were made up of individuals. The average household size was 2.36 and the average family size was 2.83. The median age was 43.2 years.
The median income for a household in the county was $41,023 and the median income for a family was $56,544. Males had a median income of $31,639 versus $26,737 for females. The per capita income for the county was $22,441. About 9.3% of families and 17.1% of the population were below the poverty line, including 27.6% of those under age 18 and 12.8% of those age 65 or over.
Marshall County voters have tended to vote Democratic for the past several decades. In 64% of the national elections since 1960, the county selected the Democratic Party candidate.