Keystone is a town in the Black Hills region of Pennington County, South Dakota, United States. The population was 337 at the 2010 census. It had its origins in 1883 as a mining town, and has since transformed itself into a resort town, serving the needs of the millions of visitors to the Mount Rushmore National Memorial, which is located just beyond city limits. Keystone was heavily damaged in the 1972 Black Hills flood.
Keystone is located at 43°53′37″N 103°25′34″W / 43.893744°N 103.426080°W / 43.893744; -103.426080.
According to the United States Census Bureau, the town has a total area of 2.86 square miles (7.41 km), all of it land.
Keystone has been assigned the ZIP code 57751 and the FIPS place code 33820.
As of the census of 2010, there were 337 people, 153 households, and 81 families residing in the town. The population density was 117.8 inhabitants per square mile (45.5/km). There were 230 housing units at an average density of 80.4 per square mile (31.0/km). The racial makeup of the town was 93.8% White, 3.3% Native American, 0.6% Asian, 0.3% Pacific Islander, 0.3% from other races, and 1.8% from two or more races. Hispanic or Latino of any race were 8.3% of the population.
There were 153 households of which 23.5% had children under the age of 18 living with them, 39.2% were married couples living together, 8.5% had a female householder with no husband present, 5.2% had a male householder with no wife present, and 47.1% were non-families. 34.0% of all households were made up of individuals and 10.4% had someone living alone who was 65 years of age or older. The average household size was 2.20 and the average family size was 2.83.
The median age in the town was 42.8 years. 22.3% of residents were under the age of 18; 3.8% were between the ages of 18 and 24; 27.5% were from 25 to 44; 33.5% were from 45 to 64; and 12.8% were 65 years of age or older. The gender makeup of the town was 50.7% male and 49.3% female.
As of the census of 2000, there were 311 people, 152 households, and 84 families residing in the town. The population density was 108.6 people per square mile (42.0/km). There were 209 housing units at an average density of 73.0 per square mile (28.2/km). The racial makeup of the town was 95.50% White, 1.93% Native American, 0.32% from other races, and 2.25% from two or more races. Hispanic or Latino of any race were 3.54% of the population.
There were 152 households out of which 27.0% had children under the age of 18 living with them, 37.5% were married couples living together, 12.5% had a female householder with no husband present, and 44.1% were non-families. 35.5% of all households were made up of individuals and 11.8% had someone living alone who was 65 years of age or older. The average household size was 2.05 and the average family size was 2.60.
In the town, the population was spread out with 20.9% under the age of 18, 5.8% from 18 to 24, 30.9% from 25 to 44, 30.9% from 45 to 64, and 11.6% who were 65 years of age or older. The median age was 41 years. For every 100 females, there were 89.6 males. For every 100 females age 18 and over, there were 95.2 males.
As of 2000 the median income for a household in the town was $26,406, and the median income for a family was $36,250. Males had a median income of $24,219 versus $17,500 for females. The per capita income for the town was $15,828. About 13.9% of families and 16.9% of the population were below the poverty line, including 17.9% of those under age 18 and 23.3% of those age 65 or over.