In a frontier town, the presence of a jail was a sure sign of civilization. In 1878, when the county seat was moved from Sheridan to Rapid City, Sheriff Moulton designated the Rapid City Jail inside the Pennington County Courthouse. Prior to that, the jail was a log shack located at the corner of Sixth and St. Joseph Streets that housed federal prisoners and town drunks. After two fires, in 1921 county voters approved a bond issue for a new courthouse and jail at a cost of $500,000.

The Sheriff and his family lived in an apartment on the second floor of the “old jail”. The deputy had an apartment on the first. There was a 16 person cell block on each floor for a total capacity of 32. Males stayed in one cell and females and children in the other. The boiler and kitchen were in the basement. The Sheriff’s family had the contract for feeding the inmates.

The first floor apartment was take out in 1960 to accommodate two cells for juveniles—male and female. Over the years as Pennington County grew, four sleeping bunks were added to each side of each cell. The space was so tight only one person could stand at a time. On busy weekends, as many as could fit were squeezed into cells.

In 1971, a jail addition was added to the 1921 facility along with a remodel. Two maximum security cell blocks and three other cells were added to meet the rising needs of a growing community. The maximum security blocks were "state of the art", with separate cubicles that could be locked down, independent of the others. This was accomplished with a lever system to slide the doors open and closed. These cells were constructed of heavy steel bars. Jail capacity was determined by how many bunks would fit in the area available. Juveniles were moved to the second floor.

The first national jail census in 1971 records 51 daily inmates. Eventually juveniles were moved to another facility. The jail population continued to climb to more than 100 a day, and in 1980, two prisoners sued Pennington County for overcrowding and adverse living conditions. By 1984, by court order, Pennington County inmates were being shipped to Meade, Hughes and Minnehaha Counties. Circuit judges ruled the 62 bed facility was not sufficient space for the number of prisoners.

Calling it a crisis, Sheriff Don Holloway lead the charge to build a new generation jail, with pods and direct supervision of larger numbers of inmates. Voters turned down $9.665 million bond issue in 1985. A modular building was constructed in the parking lot to accommodate 42 male minimum security inmates. In 1986 a compact was formed to borrow about $12.5 million for the new jail. In 1988 the daily inmate count surpassed 100.

After two years of construction, a new $10.2 million jail opened in 1989, more than doubling previous available jail space. With 90,000 square feet and a capacity of 236 prisoners, Pennington County rented out space to the South Dakota State Penitentiary, other counties and the US Marshal.

The jail population continued to climb. In 1995, the inmate count surpasses 200. In 1999, the jail was reconfigured to raise the inmate capacity from 236 to 276. Just ten years after renting space, the jail again began to send overflow inmates to other counties. By 2000 jail overcrowding was again a problem.

The compact again borrowed money for a new jail expansion. In the fall of 2006, a four-story multi-level security facility opened, eventually accommodating 328 beds. This new facility is referred to as the jail annex and it connects to the original jail. Medical facilities were added to the $10.2 million annex.

By 2014 the jail daily inmate count surpassed 400. In 2015, Pennington County, with its 624 bed jail complex, was selected as a finalist for a MacArthur Foundation grant project to safely reduce jail populations for low-level offenders. In 2017, $1.75 million was awarded for the Safety + Justice Challenge.

The Pennington County Jail continues to embrace progress as it adapts to meet the ever changing needs of the citizens of Pennington County. After several years of planning, Pennington County is moving forward in 2018 with a project to replace the 30 year old kitchen and laundry facilities and adjust staff and administrative facilities to meet the demands of the 662 adult inmate space, 53 juvenile detainees served and close to 80 drug and alcohol treatment clients served by our facility.