Pennington County, South Dakota

Pennington County is a county in South Dakota, United States, straddling the eastern edge of the Black Hills and stretching out onto the Badlands prairie. It had a population of 109,222 at the 2020 census and covers 2,777 square miles (7,190 km2) of land centred near 44°00′N 102°49′W.

Rapid City is the county seat and largest city; its postal code is 57701. The county holds 4 cities, 4 incorporated towns, and roughly four dozen unincorporated communities and subdivisions, most of them small residential “additions” tucked into the pine-covered hills west of Rapid City. Pennington County has no organized civil townships. It observes Mountain Time, unlike most of South Dakota, which runs on Central Time.

Towns & Villages in Pennington County

Rapid City dominates the county’s population; Box Elder, adjoining Ellsworth Air Force Base, is a distant second. The remaining incorporated towns sit either up in the Black Hills (Hill City, Keystone) or out on the prairie (New Underwood, Quinn, Wall, Wasta). Everything else below is unincorporated — Census-designated places (CDP) or small GNIS-listed subdivisions and hamlets (Unincorp.) with no municipal government of their own.

Two names from older lists were dropped as not distinct GNIS-recognized places: “Gossage Memorial” and “Ridgeland Heights Addition” duplicate entries elsewhere in the county’s populated-place records and are folded into their parent subdivisions above.

ZIP Codes

• 57701–57709 — Rapid City (also serves Rapid Valley, Rockerville, and most unincorporated hill country immediately around the city)
• 57719 — Box Elder
• 57725 — Caputa
• 57745 — Hill City
• 57751 — Keystone
• 57761 — New Underwood
• 57775 — Quinn
• 57790 — Wall
• 57791 — Wasta

Most of the small subdivisions and ghost-town sites scattered through the Black Hills backcountry, such as Rochford, Mystic, and Silver City, use a Rapid City or Hill City ZIP for mail rather than one of their own.

Geography

Pennington County splits into two very different landscapes. The western half climbs into the granite spires and ponderosa-pine forest of the Black Hills, topping out at Black Elk Peak — at 7,242 feet the highest point in the United States east of the Rocky Mountains. The eastern half drops onto the mixed-grass prairie and eroded buttes of the Badlands, including the northern unit of Badlands National Park and the Sage Creek Wilderness Area. Rapid Creek, French Creek, and Battle Creek drain the Black Hills side; the Cheyenne River crosses the county’s eastern reaches.

Pennington County borders Meade County to the north, Haakon County to the northeast, Jackson County to the east, Oglala Lakota County to the south, Custer County to the southwest, Fall River County to the south-southwest, and Weston County, Wyoming, across the state line to the west.

Demographics

Pennington County counted 109,222 residents at the 2020 census, South Dakota’s second most populous county after Minnehaha. Rapid City and Box Elder are by far the two largest communities; together they hold more than three-quarters of the county’s population. Median household income runs below the South Dakota median of $71,810, reflecting the mix of a service- and tourism-heavy Rapid City economy with lower-income rural areas to the east. Overall density works out to roughly 39 people per square mile, though that figure masks a dense urban core around Rapid City and vast, nearly empty ranch and grassland country toward the Badlands.

Economy & Local Life

Ellsworth Air Force Base, home to the Air Force’s B-1B Lancer bomber fleet, is the county’s largest single employer and anchors Box Elder’s growth. Rapid City itself carries the county’s healthcare, retail, and government jobs, plus a large tourism sector built on Mount Rushmore, the Black Hills, and Badlands National Park — millions of visitors pass through the county every summer on their way to those parks. The South Dakota School of Mines and Technology, in Rapid City, is the state’s engineering and science university. Ranching and hay production carry the prairie townships east of Wall and Scenic.

History

Pennington County was created on January 11, 1875, and organized on April 19, 1877, named for John L. Pennington, the fifth governor of Dakota Territory, who held that office when the county was formed. Its creation followed the 1874 Black Hills Expedition and the gold rush that brought thousands of prospectors into Lakota treaty land, triggering the conflict that ended with the Black Hills’ seizure from the Sioux Nation in 1877. Rapid City was platted in 1876 as a supply town for the mining camps to the west. Ellsworth Air Force Base traces to 1942, when the Army Air Forces built Rapid City Army Air Base as a heavy-bomber training field; it was renamed in 1953 for Brigadier General Richard Ellsworth.

Getting There

Interstate 90 runs east–west through Box Elder and Rapid City, the county’s main highway corridor. US 16 heads southwest from Rapid City toward Mount Rushmore, Keystone, and Custer; US 385 runs north–south through Hill City and Deerfield; SD Highway 44 and SD 79 serve the southern and eastern parts of the county.

• Rapid City — county seat, on I-90
• Sturgis — about 30 miles north, in Meade County
• Custer — about 45 miles southwest, via US 16/385
• Wall — about 55 miles east, on I-90 at the edge of the Badlands

Rapid City Regional Airport (RAP), southeast of the city, is the region’s commercial airport, with direct flights to several major hubs.

Frequently Asked Questions

Where is Pennington County, South Dakota?
It sits in the western part of South Dakota, spanning the eastern Black Hills and the western edge of the Badlands, with Wyoming forming part of its western border.

What is the population of Pennington County?
109,222 at the 2020 census, South Dakota’s second most populous county.

How big is Pennington County?
2,777 square miles (7,190 km2) of land, the third-largest land area of any South Dakota county.

What is the county seat of Pennington County?
Rapid City is the county seat and by far its largest city.

How many towns are in Pennington County?
Four cities (Rapid City, Box Elder, Hill City, New Underwood) and four incorporated towns (Keystone, Quinn, Wall, Wasta), plus close to fifty unincorporated communities and subdivisions.

What ZIP codes are in Pennington County?
Rapid City uses 57701 through 57709; outlying towns each carry their own code, from 57719 in Box Elder to 57791 in Wasta.

Where is Mount Rushmore in relation to the county?
Mount Rushmore National Memorial sits in the Black Hills near Keystone, in the southwestern part of Pennington County.

More counties in this state: Towns and villages in South Dakota.