| | Mossyrock, WA | Elma, WA | United States |
| Population | 739 | 3,390 | 329,725,481 |
| Female Population | 55.5% | 53.1% | 50.5% |
| Male Population | 44.5% | 46.9% | 49.5% |
| Median Age | 31.4 | 41.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 759 | 3,294 | 309,327,143 |
| Population - 2000 | 486 | 3,049 | 285,036,114 |
| Population - 1990 | 452 | 3,011 | 251,960,433 |
| Pop. 2000 to Now | 72.4% | 10.8% | 15.6% |
| Pop. 1990 to Now | 85.4% | 12.2% | 30.8% |
| space4 | | | |
| Population Density | 1,078.8 | 1,329.4 | 93.4 |
| Land Area | 0.7 | 2.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Mossyrock, WA | Elma, WA | United States |
| Age 0 to 4 | 10.0% | 5.5% | 5.9% |
| Age 5 to 9 | 14.1% | 3.8% | 6.1% |
| Age 10 to 14 | 8.4% | 8.0% | 6.6% |
| Age 15 to 17 | 3.8% | 0.9% | 3.9% |
| Age 18 to 20 | 1.8% | 3.8% | 4.0% |
| Age 21 to 24 | 1.2% | 5.6% | 5.2% |
| Age 25 to 34 | 15.7% | 12.0% | 13.8% |
| Age 35 to 44 | 11.5% | 12.6% | 12.9% |
| Age 45 to 54 | 8.0% | 6.9% | 12.6% |
| Age 55 to 59 | 5.5% | 6.4% | 6.7% |
| Age 60 to 64 | 4.3% | 12.4% | 6.3% |
| Age 65 to 74 | 10.8% | 14.1% | 9.6% |
| Age 75 to 84 | 4.7% | 7.9% | 4.5% |
| Age 85 and over | 0.1% | 0.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Mossyrock, WA | Elma, WA | United States |
| White | 54.1% | 92.7% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 0.0% | 0.5% | 5.6% |
| Native American | 0.9% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 10.7% | 3.6% | 3.2% |
| Hispanic | 34.2% | 3.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Mossyrock, WA | Elma, WA | United States |
| Married Population | 68.5% | 53.4% | 49.8% |
| Currently Married | 60.7% | 51.5% | 48.0% |
| Married but Separated | 7.8% | 1.8% | 1.8% |
| Single Population | 31.5% | 46.6% | 50.2% |
| Never Married | 19.0% | 23.7% | 33.8% |
| Divorced | 5.2% | 18.0% | 10.8% |
| Widowed | 7.2% | 4.9% | 5.6% |
| space5 | | | |
| Household Size | 2.93 | 2.52 | 2.60 |
| Households | 252 | 1,328 | 124,010,992 |
| Family Households | 177 | 836 | 80,755,759 |
| Married couple, w/children | 45.2% | 18.1% | 30.5% |
| Married couple, no children | 35.0% | 53.7% | 42.9% |
| Non Family Households | 75 | 492 | 43,255,233 |
| Single householder, w/children | 19.8% | 25.8% | 15.8% |
| Single householder, no children | 0.0% | 2.4% | 10.8% |