| | Challis, ID | Arco, ID | United States |
| Population | 891 | 742 | 329,725,481 |
| Female Population | 50.7% | 60.7% | 50.5% |
| Male Population | 49.3% | 39.4% | 49.5% |
| Median Age | 43.8 | 37.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,093 | 990 | 309,327,143 |
| Population - 2000 | 909 | 1,026 | 285,036,114 |
| Population - 1990 | 1,073 | 1,016 | 251,960,433 |
| Pop. 2000 to Now | 17.3% | -13.0% | 15.6% |
| Pop. 1990 to Now | -0.7% | -12.1% | 30.8% |
| space4 | | | |
| Population Density | 464.3 | 694.8 | 93.4 |
| Land Area | 1.9 | 1.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Challis, ID | Arco, ID | United States |
| Age 0 to 4 | 4.8% | 6.2% | 5.9% |
| Age 5 to 9 | 10.7% | 14.7% | 6.1% |
| Age 10 to 14 | 8.1% | 5.7% | 6.6% |
| Age 15 to 17 | 2.2% | 3.6% | 3.9% |
| Age 18 to 20 | 0.7% | 3.4% | 4.0% |
| Age 21 to 24 | 5.8% | 2.3% | 5.2% |
| Age 25 to 34 | 8.6% | 9.4% | 13.8% |
| Age 35 to 44 | 12.7% | 11.2% | 12.9% |
| Age 45 to 54 | 17.8% | 5.8% | 12.6% |
| Age 55 to 59 | 8.1% | 6.3% | 6.7% |
| Age 60 to 64 | 6.3% | 10.9% | 6.3% |
| Age 65 to 74 | 11.9% | 11.1% | 9.6% |
| Age 75 to 84 | 1.7% | 6.5% | 4.5% |
| Age 85 and over | 0.6% | 3.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Challis, ID | Arco, ID | United States |
| White | 82.6% | 90.4% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.1% | 0.0% | 5.6% |
| Native American | 2.5% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 3.0% | 0.0% | 0.4% |
| Two or More Races | 1.2% | 7.1% | 3.2% |
| Hispanic | 10.6% | 2.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Challis, ID | Arco, ID | United States |
| Married Population | 49.3% | 52.8% | 49.8% |
| Currently Married | 46.4% | 52.8% | 48.0% |
| Married but Separated | 2.9% | 0.0% | 1.8% |
| Single Population | 50.7% | 47.2% | 50.2% |
| Never Married | 24.5% | 14.9% | 33.8% |
| Divorced | 25.4% | 24.8% | 10.8% |
| Widowed | 0.7% | 7.5% | 5.6% |
| space5 | | | |
| Household Size | 2.48 | 2.71 | 2.60 |
| Households | 346 | 263 | 124,010,992 |
| Family Households | 150 | 170 | 80,755,759 |
| Married couple, w/children | 38.7% | 24.7% | 30.5% |
| Married couple, no children | 36.0% | 49.4% | 42.9% |
| Non Family Households | 196 | 93 | 43,255,233 |
| Single householder, w/children | 12.0% | 17.6% | 15.8% |
| Single householder, no children | 13.3% | 8.2% | 10.8% |