Pennington County, South Dakota

Pennington County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 109,222, making it the second most populous county in South Dakota, and was estimated to be 116,792 in 2025. The county was created on January 11, 1875, and was organized on April 19, 1877. It is named for John L. Pennington, fifth Governor of Dakota Territory, who held office in 1875 when the county was formed. Pennington County is included in the Rapid City metropolitan statistical area. It is also the location of Mount Rushmore.

History

In 1874, US Army commander George A. Custer led a group into the Black Hills area. He and some of his officers climbed the crest now called Black Elk Peak, and made a toast to US General William S. Harney. They named the peak for Harney, and this name was used until 2016. This expedition reported that gold could be found in the Black Hills, which spurred a gold rush into the future county area. The mining settlements that sprang up were in violation of the second Treaty of Fort Laramie signed with the Sioux Nation in 1868. By 1875, settlement was sufficient to justify creation of a local governing organization, so Pennington County was created on January 11, 1875, and it was fully organized by April 19, 1877. The county's boundaries were adjusted in 1877 and in 1898.

The county seat was initially at Sheridan, a mining camp. (Sheridan is credited with hosting the first Federal Court west of the Missouri River.) In 1878, the county seat was moved to Rapid City.

In 1923, Doane Robinson, superintendent of the SD State Historical Society, began promoting the concept of a giant sculpture carved from a Black Hills mountain. By 1927 this concept took substance, when work on Mount Rushmore began.

Shortly after the US entered World War II, an Army training airbase was established in Pennington County. It has continued until the present, now known as Ellsworth Air Force Base. Supporting this activity has provided a substantial portion of the county's economic base since that time.

Geography

thumb|Extinct [[Mesohippus horse, found in Pennington County, on display at the Houston Museum of Natural Science]]

Pennington County is located on the west line of South Dakota. Its west boundary line abuts the east boundary line of the state of Wyoming. Its west end contains the nation's highest peak east of the continental divide, Black Elk Peak. The rugged arid western end contains forest and gullies, descendending to rough rolling hill country in the east. The Cheyenne River flows north-northeastward through the center of the county and then along its northeastern border on its way to discharge in the Missouri River, while Rapid Creek flows east-southeastward through the western part, to discharge into the Cheyenne at the county's midpoint. The county terrain varies in elevation from Black Elk Peak at to its NE corner, at ASL.

According to the United States Census Bureau, the county has a total area of , of which is land and (0.28%) is water. It is the third-largest county in South Dakota by total area, and is larger than the state of Delaware.

Major highways

20px Interstate 90
20px U.S. Highway 14
20px U.S. Highway 16
25px U.S. Highway 16A
25px U.S. Highway 385
20px South Dakota Highway 40
20px South Dakota Highway 44
25px South Dakota Highway 240
25px South Dakota Highway 244

Transit

Jefferson Lines
Rapid City Rapid Ride

Adjacent counties

Meade County – north
Ziebach County – northeast
Haakon County – northeast
Jackson County – southeast
Oglala Lakota County – south
Custer County – southwest
Weston County, Wyoming – west
Lawrence County – northwest

National protected areas

Badlands National Park (part)
Badlands Wilderness
Black Hills National Forest (part)
Black Elk Wilderness (part)
Buffalo Gap National Grassland (part)
Minuteman Missile National Historic Site (part)
Mount Rushmore National Memorial

Lakes and reservoirs

Source:

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|footnote=U.S. Decennial Census 1790–1960 1900–1990 1990–2000 2010–2020

As of the 2023 American Community Survey, there are 45,698 estimated households in Pennington County with an average of 2.37 persons per household. The county has a median household income of $70,768. Approximately 11.6% of the county's population lives at or below the poverty line. Pennington County has an estimated 63.0% employment rate, with 34.1% of the population holding a bachelor's degree or higher and 94.7% holding a high school diploma.

The median age in the county was 40.2 years.

Pennington County, South Dakota – racial and ethnic composition

{| class="wikitable sortable collapsible" style="font-size: 95%;"

! Race / ethnicity (NH = non-Hispanic)

! Pop. 1980 !! Pop. 1990 !! Pop. 2010 !!

| White alone (NH)

| 64,148 (91.17%) || 71,882 (88.37%) || 75,797 (85.58%) || 82,438 (81.66%) || style='background: #ffffe6; |82,743 (75.76%)

| Black or African American alone (NH)

| 875 (1.24%) || 1,249 (1.54%) || 722 (0.82%) || 1,013 (1.00%) || style='background: #ffffe6; |1,363 (1.25%)

| Native American or Alaska Native alone (NH)

| 3,643 (5.18%) || 5,518 (6.78%) || 6,773 (7.65%) || 9,042 (8.96%) || style='background: #ffffe6; |10,927 (10.00%)

| Asian alone (NH)

| 360 (0.51%) || 884 (1.09%) || 763 (0.86%) || 1,041 (1.03%) || style='background: #ffffe6; |1,463 (1.34%)

| Pacific Islander alone (NH)

| — || — || 51 (0.06%) || 76 (0.08%) || style='background: #ffffe6; |78 (0.07%)

| Other race alone (NH)

| 91 (0.13%) || 33 (0.04%) || 66 (0.07%) || 71 (0.07%) || style='background: #ffffe6; |411 (0.38%)

| Mixed race or multiracial (NH)

| — || — || 2,052 (2.32%) || 3,223 (3.19%) || style='background: #ffffe6; |6,662 (6.10%)

| Hispanic or Latino (any race)

| 1,244 (1.77%) || 1,777 (2.18%) || 2,341 (2.64%) || 4,044 (4.01%) || style='background: #ffffe6; |5,575 (5.10%)

| Total

| 70,361 (100.00%) || 81,343 (100.00%) || 88,565 (100.00%) || 100,948 (100.00%) || style='background: #ffffe6; |109,222 (100.00%)

2020 census

As of the 2020 census, there were 109,222 people, 44,909 households, and 27,584 families residing in the county. Of the residents, 22.4% were under the age of 18 and 18.6% were 65 years of age or older; the median age was 38.9 years. For every 100 females there were 100.8 males, and for every 100 females age 18 and over there were 99.5 males.

The population density was , and there were 49,153 housing units at an average density of . The racial makeup of the county was 77.4% White, 1.3% African American, 10.7% Native American, 1.4% Asian, 0.08% Pacific Islander, 1.3% from some other races, and 7.9% from two or more races. Hispanic or Latino people of any race were 5.1% of the population. The sheriff's office issues concealed pistol permits to county residents. The current Sheriff is Brian Mueller.

The Sheriff's Office also operates the Pennington County Search and Rescue (PCSAR) team, a volunteer search and rescue (SAR) team based in Rapid City, was established in 1973, prompted by a 1972 flood in Rapid City. It serves residents and tourists in the county and the Black Hills area.

Communities

Cities

Box Elder
Hill City
New Underwood
Rapid City (county seat)

Towns

Keystone
Quinn
Wall
Wasta

Census-designated places

Ashland Heights
Caputa
Colonial Pine Hills
Green Valley
Johnson Siding
Rapid Valley

Unincorporated communities