Todd County is one of two counties in South Dakota that does not have its own county seat (Shannon County is the other). Winner in neighboring Tripp County serves as its administrative center. It is also one of five South Dakota counties that lie entirely within an Indian reservation. (The others are Corson, Dewey, Shannon, and Ziebach.)
As of the census of 2000, there were 9,050 people, 2,462 households, and 1,917 families residing in the county. The population density was 6 people per square mile (3/km²). There were 2,766 housing units at an average density of 2 per square mile (1/km²). The racial makeup of the county was 85.60% Native American, 12.57% White, 0.09% Black or African American, 0.14% Asian, 0.21% from other races, and 1.38% from two or more races. 1.52% of the population were Hispanic or Latino of any race.
There were 2,462 households out of which 48.90% had children under the age of 18 living with them, 35.20% were married couples living together, 31.80% had a female householder with no husband present, and 22.10% were non-families. 18.90% of all households were made up of individuals and 5.20% had someone living alone who was 65 years of age or older. The average household size was 3.62 and the average family size was 4.09.
In the county, the population was spread out with 44.00% under the age of 18, 10.40% from 18 to 24, 25.10% from 25 to 44, 14.80% from 45 to 64, and 5.80% who were 65 years of age or older. The median age was 22 years. For every 100 females there were 97.90 males. For every 100 females age 18 and over, there were 92.30 males.
The median income for a household in the county was $20,035, and the median income for a family was $19,533. Males had a median income of $20,993 versus $21,449 for females. The per capita income for the county was $7,714. About 44.00% of families and 48.30% of the population were below the poverty line, including 57.60% of those under age 18 and 33.50% of those age 65 or over. The county's per-capita income makes it one of the poorest counties in the United States.