Pennington County, South Dakota: 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.