| | Waterville, WA | Tonasket, WA | United States |
| Population | 1,461 | 980 | 329,725,481 |
| Female Population | 44.5% | 49.3% | 50.5% |
| Male Population | 55.5% | 50.7% | 49.5% |
| Median Age | 49.9 | 47.1 | 38.4 |
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| Population - 2010 | 1,139 | 1,147 | 309,327,143 |
| Population - 2000 | 1,163 | 994 | 285,036,114 |
| Population - 1990 | 995 | 847 | 251,960,433 |
| Pop. 2000 to Now | 2.9% | 13.8% | 15.6% |
| Pop. 1990 to Now | 20.3% | 33.5% | 30.8% |
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| Population Density | 1,685.1 | 1,034.9 | 93.4 |
| Land Area | 0.9 | 0.9 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Waterville, WA | Tonasket, WA | United States |
| Age 0 to 4 | 5.3% | 5.3% | 5.9% |
| Age 5 to 9 | 3.9% | 7.7% | 6.1% |
| Age 10 to 14 | 3.5% | 3.4% | 6.6% |
| Age 15 to 17 | 2.3% | 2.4% | 3.9% |
| Age 18 to 20 | 3.5% | 3.6% | 4.0% |
| Age 21 to 24 | 4.7% | 1.0% | 5.2% |
| Age 25 to 34 | 10.7% | 10.2% | 13.8% |
| Age 35 to 44 | 11.2% | 11.2% | 12.9% |
| Age 45 to 54 | 14.5% | 18.7% | 12.6% |
| Age 55 to 59 | 10.8% | 7.3% | 6.7% |
| Age 60 to 64 | 10.5% | 6.6% | 6.3% |
| Age 65 to 74 | 14.2% | 10.1% | 9.6% |
| Age 75 to 84 | 2.2% | 6.8% | 4.5% |
| Age 85 and over | 2.8% | 5.6% | 1.9% |
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| Race | | | |
| | Waterville, WA | Tonasket, WA | United States |
| White | 81.2% | 72.2% | 59.4% |
| Black | 0.3% | 0.0% | 12.2% |
| Asian | 0.0% | 0.0% | 5.6% |
| Native American | 0.0% | 1.5% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.5% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 5.1% | 12.8% | 3.2% |
| Hispanic | 13.4% | 13.0% | 18.4% |
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| Marriage & Family | | | |
| | Waterville, WA | Tonasket, WA | United States |
| Married Population | 61.3% | 53.7% | 49.8% |
| Currently Married | 61.3% | 47.6% | 48.0% |
| Married but Separated | 0.0% | 6.1% | 1.8% |
| Single Population | 38.7% | 46.3% | 50.2% |
| Never Married | 27.3% | 15.2% | 33.8% |
| Divorced | 5.3% | 19.0% | 10.8% |
| Widowed | 6.2% | 12.1% | 5.6% |
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| Household Size | 2.48 | 2.14 | 2.60 |
| Households | 584 | 433 | 124,010,992 |
| Family Households | 421 | 216 | 80,755,759 |
| Married couple, w/children | 22.6% | 32.9% | 30.5% |
| Married couple, no children | 60.6% | 48.6% | 42.9% |
| Non Family Households | 163 | 217 | 43,255,233 |
| Single householder, w/children | 8.6% | 16.2% | 15.8% |
| Single householder, no children | 8.3% | 2.3% | 10.8% |