| | Sun Valley, ID | Custer, SD | United States |
| Population | 1,277 | 2,067 | 329,725,481 |
| Female Population | 52.7% | 51.8% | 50.5% |
| Male Population | 47.3% | 48.2% | 49.5% |
| Median Age | 58 | 57.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,405 | 2,015 | 309,327,143 |
| Population - 2000 | 1,427 | 1,860 | 285,036,114 |
| Population - 1990 | 938 | 1,741 | 251,960,433 |
| Pop. 2000 to Now | 5.3% | 3.6% | 15.6% |
| Pop. 1990 to Now | 60.2% | 10.6% | 30.8% |
| space4 | | | |
| Population Density | 133.5 | 817.0 | 93.4 |
| Land Area | 9.6 | 2.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Sun Valley, ID | Custer, SD | United States |
| Age 0 to 4 | 2.5% | 4.0% | 5.9% |
| Age 5 to 9 | 2.3% | 4.4% | 6.1% |
| Age 10 to 14 | 0.0% | 3.8% | 6.6% |
| Age 15 to 17 | 5.5% | 2.0% | 3.9% |
| Age 18 to 20 | 3.4% | 3.3% | 4.0% |
| Age 21 to 24 | 6.3% | 3.1% | 5.2% |
| Age 25 to 34 | 3.4% | 6.6% | 13.8% |
| Age 35 to 44 | 4.6% | 7.6% | 12.9% |
| Age 45 to 54 | 17.5% | 13.5% | 12.6% |
| Age 55 to 59 | 6.7% | 6.3% | 6.7% |
| Age 60 to 64 | 6.0% | 9.3% | 6.3% |
| Age 65 to 74 | 30.0% | 18.1% | 9.6% |
| Age 75 to 84 | 8.9% | 12.5% | 4.5% |
| Age 85 and over | 2.7% | 5.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Sun Valley, ID | Custer, SD | United States |
| White | 83.2% | 86.5% | 59.4% |
| Black | 1.6% | 3.1% | 12.2% |
| Asian | 0.4% | 0.4% | 5.6% |
| Native American | 0.0% | 4.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.2% | 0.0% | 0.4% |
| Two or More Races | 5.1% | 1.1% | 3.2% |
| Hispanic | 9.6% | 4.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Sun Valley, ID | Custer, SD | United States |
| Married Population | 48.8% | 54.4% | 49.8% |
| Currently Married | 48.1% | 54.4% | 48.0% |
| Married but Separated | 0.7% | 0.0% | 1.8% |
| Single Population | 51.2% | 45.6% | 50.2% |
| Never Married | 23.5% | 20.8% | 33.8% |
| Divorced | 23.2% | 16.3% | 10.8% |
| Widowed | 4.5% | 8.4% | 5.6% |
| space5 | | | |
| Household Size | 2.00 | 1.97 | 2.60 |
| Households | 513 | 977 | 124,010,992 |
| Family Households | 249 | 626 | 80,755,759 |
| Married couple, w/children | 16.1% | 13.9% | 30.5% |
| Married couple, no children | 80.3% | 64.1% | 42.9% |
| Non Family Households | 264 | 351 | 43,255,233 |
| Single householder, w/children | 0.0% | 13.9% | 15.8% |
| Single householder, no children | 3.6% | 8.1% | 10.8% |