| | Eagle Butte, SD | Fort Thompson, SD | United States |
| Population | 1,421 | 1,266 | 329,725,481 |
| Female Population | 49.8% | 48.8% | 50.5% |
| Male Population | 50.2% | 51.2% | 49.5% |
| Median Age | 29.2 | 25.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,428 | 1,428 | 309,327,143 |
| Population - 2000 | 619 | 1,375 | 285,036,114 |
| Population - 1990 | 489 | 1,088 | 251,960,433 |
| Pop. 2000 to Now | 129.1% | -13.9% | 15.6% |
| Pop. 1990 to Now | 190.0% | 8.8% | 30.8% |
| space4 | | | |
| Population Density | 1,212.5 | 122.0 | 93.4 |
| Land Area | 1.2 | 10.4 | 3,531,905.4 |
| Water Area | 0.0 | 2.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Eagle Butte, SD | Fort Thompson, SD | United States |
| Age 0 to 4 | 8.3% | 11.5% | 5.9% |
| Age 5 to 9 | 9.1% | 9.6% | 6.1% |
| Age 10 to 14 | 10.3% | 8.1% | 6.6% |
| Age 15 to 17 | 7.0% | 7.3% | 3.9% |
| Age 18 to 20 | 3.7% | 8.1% | 4.0% |
| Age 21 to 24 | 4.7% | 5.5% | 5.2% |
| Age 25 to 34 | 13.4% | 11.0% | 13.8% |
| Age 35 to 44 | 20.5% | 11.8% | 12.9% |
| Age 45 to 54 | 6.5% | 9.6% | 12.6% |
| Age 55 to 59 | 4.8% | 5.4% | 6.7% |
| Age 60 to 64 | 5.9% | 7.5% | 6.3% |
| Age 65 to 74 | 2.2% | 2.6% | 9.6% |
| Age 75 to 84 | 3.0% | 2.3% | 4.5% |
| Age 85 and over | 0.6% | 0.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Eagle Butte, SD | Fort Thompson, SD | United States |
| White | 7.7% | 1.7% | 59.4% |
| Black | 0.3% | 0.0% | 12.2% |
| Asian | 0.0% | 0.0% | 5.6% |
| Native American | 78.6% | 93.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 1.7% | 0.0% | 3.2% |
| Hispanic | 11.7% | 4.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Eagle Butte, SD | Fort Thompson, SD | United States |
| Married Population | 22.7% | 25.2% | 49.8% |
| Currently Married | 21.7% | 23.8% | 48.0% |
| Married but Separated | 1.0% | 1.3% | 1.8% |
| Single Population | 77.3% | 74.8% | 50.2% |
| Never Married | 57.0% | 57.4% | 33.8% |
| Divorced | 16.3% | 10.7% | 10.8% |
| Widowed | 4.0% | 6.8% | 5.6% |
| space5 | | | |
| Household Size | 3.60 | 4.04 | 2.60 |
| Households | 387 | 313 | 124,010,992 |
| Family Households | 289 | 237 | 80,755,759 |
| Married couple, w/children | 14.9% | 14.8% | 30.5% |
| Married couple, no children | 17.3% | 14.3% | 42.9% |
| Non Family Households | 98 | 76 | 43,255,233 |
| Single householder, w/children | 54.0% | 58.7% | 15.8% |
| Single householder, no children | 13.8% | 12.2% | 10.8% |