| | Hillside, SD | Custer, SD | United States |
| Population | 40 | 2,067 | 329,725,481 |
| Female Population | 50.0% | 51.8% | 50.5% |
| Male Population | 50.0% | 48.2% | 49.5% |
| Median Age | 14.7 | 57.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 32 | 2,015 | 309,327,143 |
| Population - 2000 | 40 | 1,860 | 285,036,114 |
| Population - 1990 | 41 | 1,741 | 251,960,433 |
| Pop. 2000 to Now | -22.5% | 3.6% | 15.6% |
| Pop. 1990 to Now | -24.4% | 10.6% | 30.8% |
| space4 | | | |
| Population Density | 1.2 | 817.0 | 93.4 |
| Land Area | 34.1 | 2.5 | 3,531,905.4 |
| Water Area | 2.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Hillside, SD | Custer, SD | United States |
| Age 0 to 4 | 15.0% | 4.0% | 5.9% |
| Age 5 to 9 | 25.0% | 4.4% | 6.1% |
| Age 10 to 14 | 15.0% | 3.8% | 6.6% |
| Age 15 to 17 | 0.0% | 2.0% | 3.9% |
| Age 18 to 20 | 0.0% | 3.3% | 4.0% |
| Age 21 to 24 | 0.0% | 3.1% | 5.2% |
| Age 25 to 34 | 0.0% | 6.6% | 13.8% |
| Age 35 to 44 | 20.0% | 7.6% | 12.9% |
| Age 45 to 54 | 5.0% | 13.5% | 12.6% |
| Age 55 to 59 | 7.5% | 6.3% | 6.7% |
| Age 60 to 64 | 0.0% | 9.3% | 6.3% |
| Age 65 to 74 | 0.0% | 18.1% | 9.6% |
| Age 75 to 84 | 0.0% | 12.5% | 4.5% |
| Age 85 and over | 12.5% | 5.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Hillside, SD | Custer, SD | United States |
| White | 100.0% | 86.5% | 59.4% |
| Black | 0.0% | 3.1% | 12.2% |
| Asian | 0.0% | 0.4% | 5.6% |
| Native American | 0.0% | 4.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.0% | 1.1% | 3.2% |
| Hispanic | 0.0% | 4.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Hillside, SD | Custer, SD | United States |
| Married Population | 100.0% | 54.4% | 49.8% |
| Currently Married | 100.0% | 54.4% | 48.0% |
| Married but Separated | 0.0% | 0.0% | 1.8% |
| Single Population | 0.0% | 45.6% | 50.2% |
| Never Married | 0.0% | 20.8% | 33.8% |
| Divorced | 0.0% | 16.3% | 10.8% |
| Widowed | 0.0% | 8.4% | 5.6% |
| space5 | | | |
| Household Size | 4.00 | 1.97 | 2.60 |
| Households | 10 | 977 | 124,010,992 |
| Family Households | 10 | 626 | 80,755,759 |
| Married couple, w/children | 40.0% | 13.9% | 30.5% |
| Married couple, no children | 60.0% | 64.1% | 42.9% |
| Non Family Households | 0 | 351 | 43,255,233 |
| Single householder, w/children | 0.0% | 13.9% | 15.8% |
| Single householder, no children | 0.0% | 8.1% | 10.8% |