Buffalo County is a county in the U.S. state of South Dakota. As of the 2010 census, the population was 1,912. Its county seat is Gann Valley which, at 14 people, is the least populous county seat in the United States. The county was created in 1864, and was organized in 1871 as part of the Dakota Territory.
The Missouri River flows southerly along the county’s western boundary. The county terrain consists of semi-arid rolling hills, generally sloping to the south and east. Some area is devoted to agriculture. The south and west parts of the county are drained by Crow Creek, which discharges into the river at the county’s SW corner. The county has a total area of 488 square miles (1,260 km), of which 471 square miles (1,220 km) is land and 16 square miles (41 km) (3.4%) is water.
As of the 2000 United States Census, there are 2,032 people, 526 households, and 422 families in the county. The population density is 4 people per square mile (2/km²). There are 602 housing units at an average density of 1.3 per square mile (0.5/km²). The racial makeup of the county is 81.59% Native American, 16.34% White, 0.10% Black or African American, 0.30% from other races, and 1.67% from two or more races. 0.89% of the population are Hispanic or Latino of any race. 8.9% were of German ancestry.
There are 526 households out of which 47.10% have children under the age of 18 living with them, 37.60% are married couples living together, 31.40% have a female householder with no husband present, and 19.80% are non-families. 16.00% of all households are made up of individuals and 5.90% have someone living alone who is 65 years of age or older. The average household size is 3.83 and the average family size is 4.23.
The county population contains 41.30% under the age of 18, 11.00% from 18 to 24, 25.00% from 25 to 44, 16.10% from 45 to 64, and 6.50% who are 65 years of age or older. The median age is 23 years. For every 100 females there are 105.50 males. For every 100 females age 18 and over, there are 98 males.
The median income for a household in the county was $12,692, and the median income for a family was $14,167. Males had a median income of $18,650 versus $19,554 for females. The per capita income for the county was $5,213, the lowest in the nation. About 55.70% of families and 56.90% of the population were below the poverty line, including 61.50% of those under age 18 and 50.40% of those age 65 or over.
As of the 2010 United States Census, there were 1,912 people, 532 households, and 407 families in the county. The population density was 4.1 inhabitants per square mile (1.6/km). There were 609 housing units at an average density of 1.3 per square mile (0.50/km). The racial makeup of the county was 84.0% Native American, 14.8% white, 0.2% black or African American, 0.1% Asian, 0.0% from other races, and 0.9% from two or more races. Those of Hispanic or Latino origin made up 1.8% of the population. In terms of ancestry, 5.6% were German, and 0.0% were American.
Of the 532 households, 55.6% had children under the age of 18 living with them, 33.1% were married couples living together, 33.1% had a female householder with no husband present, 23.5% were non-families, and 19.0% of all households were made up of individuals. The average household size was 3.59 and the average family size was 4.06. The median age was 25.0 years.
The median income for a household in the county was $27,926 and the median income for a family was $28,333. Males had a median income of $38,920 versus $18,542 for females. The per capita income for the county was $11,410. About 44.4% of families and 49.3% of the population were below the poverty line, including 58.2% of those under age 18 and 36.3% of those age 65 or over.