Pennington County is a county in the U.S. state of South Dakota. As of the 2010 United States Census, the population was 100,948, making it the second-most populous county in South Dakota. Its county seat is Rapid City. The county was created in 1875, and was organized in 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 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 7,242′ (2207m) to its NE corner, at 1,896′ (578m) ASL.
Pennington County has a total area of 2,784 square miles (7,210 km), of which 2,777 square miles (7,190 km) is land and 7.7 square miles (20 km) (0.3%) is water. It is the third-largest county in South Dakota by area.
As of the 2000 United States Census, there were 88,565 people, 34,641 households, and 23,278 families in the county. The population density was 32 people per square mile (12/km²). There were 37,249 housing units at an average density of 13 per square mile (5/km²). The racial makeup of the county was 86.70% White, 0.85% Black or African American, 8.09% Native American, 0.88% Asian, 0.06% Pacific Islander, 0.68%% from other races, and 2.74% from two or more races. 2.64% of the population were Hispanic or Latino of any race.
There were 34,641 households out of which 33.50% had children under the age of 18 living with them, 51.30% were married couples living together, 11.70% had a female householder with no husband present, and 32.80% were non-families. 26.10% of all households were made up of individuals and 8.40% had someone living alone who was 65 years of age or older. The average household size was 2.49 and the average family size was 3.00.
The county population contained 26.60% under the age of 18, 10.50% from 18 to 24, 29.20% from 25 to 44, 21.90% from 45 to 64, and 11.80% who were 65 years of age or older. The median age was 35 years. For every 100 females, there were 98.30 males. For every 100 females age 18 and over, there were 95.70 males.
The median income for a household in the county was $37,485, and the median income for a family was $44,796. Males had a median income of $30,608 versus $21,540 for females. The per capita income for the county was $18,938. About 8.60% of families and 11.50% of the population were below the poverty line, including 15.60% of those under age 18 and 6.50% of those age 65 or over.
As of the 2010 United States Census, there were 100,948 people, 41,251 households, and 26,323 families in the county. The population density was 36.4 inhabitants per square mile (14.1/km). There were 44,949 housing units at an average density of 16.2 per square mile (6.3/km). The racial makeup of the county was 83.6% white, 9.7% American Indian, 1.0% black or African American, 1.0% Asian, 0.1% Pacific islander, 0.8% from other races, and 3.8% from two or more races. Those of Hispanic or Latino origin made up 4.0% of the population. In terms of ancestry, 38.0% were German, 14.3% were Irish, 11.0% were Norwegian, 10.2% were English, and 3.6% were American.
Of the 41,251 households, 31.5% had children under the age of 18 living with them, 47.1% were married couples living together, 11.7% had a female householder with no husband present, 36.2% were non-families, and 29.0% of all households were made up of individuals. The average household size was 2.38 and the average family size was 2.93. The median age was 36.8 years.
The median income for a household in the county was $46,849 and the median income for a family was $57,278. Males had a median income of $38,626 versus $30,251 for females. The per capita income for the county was $25,894. About 9.4% of families and 14.0% of the population were below the poverty line, including 20.7% of those under age 18 and 7.6% of those age 65 or over.