| County: | Lyman County |
| State: | South Dakota |
| Ex Image: | Lower brule reservation2 sd.jpg |
| Ex Image Size: | 220px |
| Founded Year: | 1893 |
| Seat Wl: | Kennebec |
| Largest City Wl: | Lower Brule |
| City Type: | community |
| Area Total Sq Mi: | 1707 |
| Area Land Sq Mi: | 1642 |
| Area Water Sq Mi: | 65 |
| Area Percentage: | 3.8 |
| Population As Of: | 2020 |
| Population Total: | 3718 |
| Pop Est As Of: | 2023 |
| Population Est: | 3705 |
| Population Density Sq Mi: | auto |
| Time Zone: | Central |
| Web: | www.lymancounty.org |
| Named For: | W. P. Lyman |
| District: | At-large |
Lyman County is a county located in the U.S. state of South Dakota. As of the 2020 census, the population was 3,718.[1] Its county seat is Kennebec.[2]
Lyman County was created by the Dakota Territorial Legislature on January 8, 1873, but was not organized until May 21, 1893. Its boundaries were altered in 1891, 1897, 1898, and 1916.[3] The county was named for W. P. Lyman, a politician.[4]
Lyman County was created in 1873 and organized in 1893.[3] Oacoma served as its first county seat in 1891; in 1922 the seat was transferred to Kennebec.[5]
Lyman County is bordered on the north and east by the Missouri River, which flows southerly along its edge, and the western portion of its south line is also delineated by the White River, which then continued flowing eastward through the county's eastern area to discharge into the Missouri. Its upper central portion is drained by the Bad Horse Creek, which discharges into the Missouri near the midpoint of the county's north boundary.
The county terrain consists of rolling hills, sloping to the river drainages. Its area is largely devoted to agriculture.[6] [7] The county has a total area of, of which is land and (3.8%) is water.[8]
As of the 2020 census, there were 3,718 people, 1,303 households, and 892 families residing in the county.[9] The population density was . There were 1,546 housing units.
As of the 2010 census, there were 3,755 people, 1,392 households, and 967 families in the county. The population density was . There were 1,704 housing units at an average density of 1.04/mi2. The racial makeup of the county was 58.3% white, 38.2% American Indian, 0.3% Asian, 0.1% black or African American, 0.1% from other races, and 2.9% from two or more races. Those of Hispanic or Latino origin made up 1.1% of the population. In terms of ancestry, 27.3% were German, 9.2% were Irish, 9.1% were Norwegian, and 1.0% were American.
Of the 1,392 households, 35.6% had children under the age of 18 living with them, 47.1% were married couples living together, 15.2% had a female householder with no husband present, 30.5% were non-families, and 27.2% of all households were made up of individuals. The average household size was 2.67 and the average family size was 3.19. The median age was 36.1 years.
The median income for a household in the county was $36,323 and the median income for a family was $45,045. Males had a median income of $32,760 versus $25,512 for females. The per capita income for the county was $16,930. About 17.4% of families and 18.8% of the population were below the poverty line, including 25.4% of those under age 18 and 5.8% of those age 65 or over.
Lyman County voters have been Republican for decades. In no national election has the county selected a Democratic Party candidate since 1964, although Jimmy Carter, Michael Dukakis, Bill Clinton, John Kerry, and Barack Obama have all managed to exceed forty percent. When Hillary Clinton ran on the Democratic ticket in 2016, she won 26 percent of the county's vote, for the lowest Democratic result since Alton B. Parker in 1904 (22 percent).