# Clay County, South Dakota

Clay County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 14,967, and was estimated to be 15,245 in 2024. The county seat is Vermillion, which is also home to the University of South Dakota. The county is named for Henry Clay, American statesman, US Senator from Kentucky, and United States Secretary of State in the 19th century. Clay County comprises the Vermillion, SD Micropolitan Statistical Area, which is also included in the Sioux City-Vermillion, Iowa-SD-Nebraska Combined Statistical Area.

## History

The future Clay County area was opened for legal settlement in 1859. In Autumn 1859, Ahira A. Partridge (who would become the first elected sheriff of the county) crossed the Missouri river into the Dakota territory, and became the first white man to settle, on 160 acres of land that now underlies Vermillion. In 1862 the county was formally organized. The Clay County Courthouse was built in 1912.
Clay County is the name of 17 other counties in the United States, most of them named for Henry Clay.

## Geography

Clay County lies on the south line of South Dakota. The south boundary line of Clay County abuts the north line of the state of Nebraska (across the Missouri River). The Missouri River flows southeast along the south boundary line of Clay County. A small drainage creek flows into the county from Turner County, draining the central and eastern portions of the county and discharging into the river. Smaller drainages move water from the western county areas into the river. In addition to sloping into the drainage through the center of the county, the terrain generally slopes to the south. The area is largely devoted to agriculture.
According to the United States Census Bureau, the county has a total area of 417.419 square miles (1,081.11 km$^2$), of which 412.022 square miles (1,067.13 km$^2$) is land and 5.397 square miles (13.98 km$^2$) (1.3%) is water. It is the 66th largest county in South Dakota by total area. It is the smallest county by area in South Dakota.

### Adjacent counties

* Turner County - north
* Lincoln County - northeast
* Union County - east
* Dixon County, Nebraska - southeast
* Cedar County, Nebraska - southwest
* Yankton County - west

### Major highways

* South Dakota Highway 19
* South Dakota Highway 46
* South Dakota Highway 50

### Protected areas

* Missouri National Recreational River (part)
* Spirit Mound State Historic Prairie

## Demographics

As of the third quarter of 2024, the median home value in Clay County was $230,280.
As of the 2023 American Community Survey, there are 5,561 estimated households in Clay County with an average of 2.28 persons per household. The county has a median household income of $58,794. Approximately 17.5% of the county's population lives at or below the poverty line. Clay County has an estimated 66.6% employment rate, with 46.0% of the population holding a bachelor's degree or higher and 93.9% holding a high school diploma.
The top five reported ancestries (people were allowed to report up to two ancestries, thus the figures will generally add to more than 100%) were English (94.4%), Spanish (1.5%), Indo-European (1.3%), Asian and Pacific Islander (1.7%), and Other (1.0%).
The median age in the county was 24.5 years.

### 2020 census

As of the 2020 census, there were 14,967 people, 5,564 households, and 2,795 families residing in the county. The population density was 36.3 inhabitants per square mile (14.0/km$^2$). There were 6,180 housing units.

### 2010 census

As of the 2010 census, there were 13,864 people, 5,110 households, and 2,628 families in the county. The population density was 33.6 inhabitants per square mile (13.0/km$^2$). There were 5,639 housing units at an average density of 13.7 per square mile (5.3/km$^2$). The racial makeup of the county was 91.1% White, 3.1% American Indian, 1.7% Asian, 1.3% black or African American, 0.5% from other races, and 2.3% from two or more races. Those of Hispanic or Latino origin made up 2.0% of the population. In terms of ancestry, 43.9% were German, 16.4% were Norwegian, 15.8% were Irish, 8.7% were English, 5.4% were Swedish, and 1.8% were American.
Of the 5,110 households, 24.7% had children under the age of 18 living with them, 40.9% were married couples living together, 7.3% had a female householder with no husband present, 48.6% were non-families, and 32.4% of all households were made up of individuals. The average household size was 2.28 and the average family size was 2.91. The median age was 25.0 years.
The median income for a household in the county was $37,198 and the median income for a family was $61,159. Males had a median income of $37,059 versus $28,016 for females. The per capita income for the county was $19,518. About 8.0% of families and 24.0% of the population were below the poverty line, including 13.6% of those under age 18 and 6.7% of those age 65 or over.

### Racial/ethnic makeup

The racial makeup of the county was 92.78% White, 1.00% Black or African American, 2.66% Native American, 1.95% Asian, 0.01% Pacific Islander, 0.29% from other races, and 1.31% from two or more races. 0.89% of the population were Hispanic or Latino of any race. 32.0% were of German, 15.6% Norwegian, 9.9% Irish and 5.4% English ancestry.

### Religion

From 2000 Census data, over 50% consider themselves "unclaimed".
* Mainline Protestant with 3,840 is most common around 28%; mainly Lutheran;
* Catholic with 1820 comes second around 13%;
* Evangelical Protestant with 613 would be around 5%; mainly Lutheran Church–Missouri Synod and Southern Baptist.

## Education

* University of South Dakota - In 1862 the territorial legislature located the State University in Vermillion, but nothing was done until 1882 when Clay County voted $10,000 in bonds to construct a building on its campus.

## Communities
### Cities

* Irene (partial)
* Vermillion (county seat)

### Town

* Wakonda

### Census-designated places

* Burbank
* Meckling

### Unincorporated communities

* Alsen (partial)
* Dalesburg
* Greenfield
* Hub City
* Westreville

### Townships

* Bethel
* Fairview
* Garfield
* Glenwood
* Meckling
* Norway
* Pleasant Valley
* Prairie Center
* Riverside
* Spirit Mound
* Star
* Vermillion

## Politics

Largely due to the presence of the University of South Dakota, Clay County has consistently voted for Democratic Party candidates for president from 1988 onward, frequently by double digit margins. In 2000, 2016, 2020, and 2024, it was the only county in the Dakotas without a Native American majority to vote Democratic for president.
United States presidential election results for Clay County, South Dakota :
| Year | Republican | Republican | Democratic | Democratic | Third party(ies) | Third party(ies) |
| Year | No. | % | No. | % | No. | % |
| 2024 | 2,574 | 45.50% | 2,944 | 52.04% | 139 | 2.46% |
| 2020 | 2,456 | 43.10% | 3,083 | 54.11% | 159 | 2.79% |
| 2016 | 2,109 | 41.61% | 2,608 | 51.45% | 352 | 6.94% |
| 2012 | 2,147 | 41.02% | 2,955 | 56.46% | 132 | 2.52% |
| 2008 | 2,296 | 36.78% | 3,808 | 61.01% | 138 | 2.21% |
| 2004 | 2,692 | 43.87% | 3,315 | 54.03% | 129 | 2.10% |
| 2000 | 2,363 | 46.29% | 2,638 | 51.67% | 104 | 2.04% |
| 1996 | 2,008 | 36.04% | 2,980 | 53.48% | 584 | 10.48% |
| 1992 | 1,869 | 30.96% | 2,826 | 46.82% | 1,341 | 22.22% |
| 1988 | 2,307 | 44.37% | 2,859 | 54.98% | 34 | 0.65% |
| 1984 | 3,057 | 52.63% | 2,711 | 46.68% | 40 | 0.69% |
| 1980 | 3,004 | 47.56% | 2,271 | 35.96% | 1,041 | 16.48% |
| 1976 | 2,647 | 49.93% | 2,593 | 48.92% | 61 | 1.15% |
| 1972 | 2,518 | 47.05% | 2,821 | 52.71% | 13 | 0.24% |
| 1968 | 2,249 | 51.28% | 2,006 | 45.74% | 131 | 2.99% |
| 1964 | 1,802 | 40.95% | 2,599 | 59.05% | 0 | 0.00% |
| 1960 | 2,772 | 59.61% | 1,878 | 40.39% | 0 | 0.00% |
| 1956 | 2,632 | 57.72% | 1,928 | 42.28% | 0 | 0.00% |
| 1952 | 3,302 | 70.05% | 1,412 | 29.95% | 0 | 0.00% |
| 1948 | 2,228 | 51.09% | 2,080 | 47.70% | 53 | 1.22% |
| 1944 | 1,970 | 52.31% | 1,796 | 47.69% | 0 | 0.00% |
| 1940 | 2,463 | 52.08% | 2,266 | 47.92% | 0 | 0.00% |
| 1936 | 1,692 | 33.60% | 3,070 | 60.97% | 273 | 5.42% |
| 1932 | 1,514 | 32.74% | 3,040 | 65.74% | 70 | 1.51% |
| 1928 | 2,573 | 63.42% | 1,474 | 36.33% | 10 | 0.25% |
| 1924 | 1,415 | 42.30% | 492 | 14.71% | 1,438 | 42.99% |
| 1920 | 1,885 | 61.88% | 907 | 29.78% | 254 | 8.34% |
| 1916 | 1,000 | 44.52% | 1,207 | 53.74% | 39 | 1.74% |
| 1912 | 0 | 0.00% | 929 | 41.00% | 1,337 | 59.00% |
| 1908 | 1,291 | 59.94% | 803 | 37.28% | 60 | 2.79% |
| 1904 | 1,723 | 77.40% | 361 | 16.22% | 142 | 6.38% |
| 1900 | 1,387 | 56.41% | 1,037 | 42.17% | 35 | 1.42% |
| 1896 | 1,238 | 53.36% | 1,061 | 45.73% | 21 | 0.91% |
| 1892 | 918 | 53.65% | 164 | 9.59% | 629 | 36.76% |