| | Green River, WY | Helena, MT | United States |
| Population | 11,887 | 32,060 | 329,725,481 |
| Female Population | 50.1% | 51.9% | 50.5% |
| Male Population | 50.0% | 48.1% | 49.5% |
| Median Age | 39.1 | 39.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 12,406 | 28,909 | 309,327,143 |
| Population - 2000 | 11,808 | 25,780 | 285,036,114 |
| Population - 1990 | 12,711 | 24,569 | 251,960,433 |
| Pop. 2000 to Now | -0.2% | 30.9% | 15.6% |
| Pop. 1990 to Now | -7.3% | 37.3% | 30.8% |
| space4 | | | |
| Population Density | 867.7 | 1,919.2 | 93.4 |
| Land Area | 13.7 | 16.7 | 3,531,905.4 |
| Water Area | 0.3 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Green River, WY | Helena, MT | United States |
| Age 0 to 4 | 5.5% | 4.8% | 5.9% |
| Age 5 to 9 | 8.0% | 5.2% | 6.1% |
| Age 10 to 14 | 9.0% | 5.9% | 6.6% |
| Age 15 to 17 | 4.8% | 3.3% | 3.9% |
| Age 18 to 20 | 3.0% | 4.3% | 4.0% |
| Age 21 to 24 | 2.2% | 6.0% | 5.2% |
| Age 25 to 34 | 12.8% | 12.6% | 13.8% |
| Age 35 to 44 | 13.9% | 13.5% | 12.9% |
| Age 45 to 54 | 14.5% | 10.9% | 12.6% |
| Age 55 to 59 | 5.9% | 6.3% | 6.7% |
| Age 60 to 64 | 7.1% | 6.6% | 6.3% |
| Age 65 to 74 | 8.9% | 11.5% | 9.6% |
| Age 75 to 84 | 2.9% | 6.5% | 4.5% |
| Age 85 and over | 1.6% | 2.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Green River, WY | Helena, MT | United States |
| White | 80.8% | 87.9% | 59.4% |
| Black | 0.0% | 0.6% | 12.2% |
| Asian | 0.8% | 0.8% | 5.6% |
| Native American | 1.8% | 1.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 1.9% | 4.3% | 3.2% |
| Hispanic | 14.7% | 5.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Green River, WY | Helena, MT | United States |
| Married Population | 60.0% | 42.2% | 49.8% |
| Currently Married | 58.7% | 41.4% | 48.0% |
| Married but Separated | 1.3% | 0.9% | 1.8% |
| Single Population | 40.0% | 57.8% | 50.2% |
| Never Married | 21.5% | 32.4% | 33.8% |
| Divorced | 11.6% | 18.4% | 10.8% |
| Widowed | 6.9% | 6.9% | 5.6% |
| space5 | | | |
| Household Size | 2.76 | 2.03 | 2.60 |
| Households | 4,289 | 15,032 | 124,010,992 |
| Family Households | 3,136 | 7,138 | 80,755,759 |
| Married couple, w/children | 38.1% | 29.4% | 30.5% |
| Married couple, no children | 44.8% | 45.9% | 42.9% |
| Non Family Households | 1,153 | 7,894 | 43,255,233 |
| Single householder, w/children | 12.0% | 17.7% | 15.8% |
| Single householder, no children | 5.2% | 7.1% | 10.8% |