| | Mattawa, WA | Dayton, WA | United States |
| Population | 3,529 | 2,544 | 329,725,481 |
| Female Population | 49.0% | 49.3% | 50.5% |
| Male Population | 51.0% | 50.7% | 49.5% |
| Median Age | 23.6 | 52.4 | 38.4 |
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| Population - 2010 | 4,463 | 2,544 | 309,327,143 |
| Population - 2000 | 2,609 | 2,655 | 285,036,114 |
| Population - 1990 | 941 | 2,468 | 251,960,433 |
| Pop. 2000 to Now | 95.9% | -6.7% | 15.6% |
| Pop. 1990 to Now | 443.3% | 0.4% | 30.8% |
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| Population Density | 4,788.3 | 1,744.9 | 93.4 |
| Land Area | 0.7 | 1.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Mattawa, WA | Dayton, WA | United States |
| Age 0 to 4 | 8.3% | 3.7% | 5.9% |
| Age 5 to 9 | 11.3% | 3.9% | 6.1% |
| Age 10 to 14 | 9.8% | 7.7% | 6.6% |
| Age 15 to 17 | 7.1% | 2.2% | 3.9% |
| Age 18 to 20 | 9.1% | 0.9% | 4.0% |
| Age 21 to 24 | 9.1% | 3.4% | 5.2% |
| Age 25 to 34 | 12.9% | 7.9% | 13.8% |
| Age 35 to 44 | 11.1% | 10.8% | 12.9% |
| Age 45 to 54 | 10.6% | 13.4% | 12.6% |
| Age 55 to 59 | 3.8% | 9.3% | 6.7% |
| Age 60 to 64 | 3.5% | 8.8% | 6.3% |
| Age 65 to 74 | 1.9% | 14.1% | 9.6% |
| Age 75 to 84 | 1.6% | 9.7% | 4.5% |
| Age 85 and over | 0.0% | 4.2% | 1.9% |
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| Race | | | |
| | Mattawa, WA | Dayton, WA | United States |
| White | 0.5% | 79.1% | 59.4% |
| Black | 0.0% | 0.6% | 12.2% |
| Asian | 0.0% | 0.1% | 5.6% |
| Native American | 0.0% | 0.4% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 0.0% | 8.4% | 3.2% |
| Hispanic | 99.5% | 11.2% | 18.4% |
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| Marriage & Family | | | |
| | Mattawa, WA | Dayton, WA | United States |
| Married Population | 38.1% | 52.5% | 49.8% |
| Currently Married | 34.5% | 52.0% | 48.0% |
| Married but Separated | 3.5% | 0.5% | 1.8% |
| Single Population | 61.9% | 47.5% | 50.2% |
| Never Married | 53.9% | 22.3% | 33.8% |
| Divorced | 5.1% | 15.5% | 10.8% |
| Widowed | 3.0% | 9.7% | 5.6% |
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| Household Size | 4.14 | 2.00 | 2.60 |
| Households | 852 | 1,239 | 124,010,992 |
| Family Households | 771 | 768 | 80,755,759 |
| Married couple, w/children | 37.2% | 18.1% | 30.5% |
| Married couple, no children | 11.5% | 53.4% | 42.9% |
| Non Family Households | 81 | 471 | 43,255,233 |
| Single householder, w/children | 47.6% | 18.0% | 15.8% |
| Single householder, no children | 3.6% | 10.5% | 10.8% |