| | Salmon Creek, WA | Brush Prairie, WA | United States |
| Population | 19,809 | 2,738 | 329,725,481 |
| Female Population | 52.8% | 49.3% | 50.5% |
| Male Population | 47.2% | 50.7% | 49.5% |
| Median Age | 44.1 | 49.7 | 38.4 |
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| Population - 2010 | 20,037 | 2,368 | 309,327,143 |
| Population - 2000 | 16,767 | 2,384 | 285,036,114 |
| Population - 1990 | 11,989 | 2,650 | 251,960,433 |
| Pop. 2000 to Now | 36.5% | 26.9% | 15.6% |
| Pop. 1990 to Now | 90.9% | 14.1% | 30.8% |
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| Population Density | 3,121.0 | 356.3 | 93.4 |
| Land Area | 6.3 | 7.7 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Salmon Creek, WA | Brush Prairie, WA | United States |
| Age 0 to 4 | 4.9% | 6.0% | 5.9% |
| Age 5 to 9 | 5.1% | 6.6% | 6.1% |
| Age 10 to 14 | 6.7% | 5.8% | 6.6% |
| Age 15 to 17 | 4.0% | 3.7% | 3.9% |
| Age 18 to 20 | 4.0% | 2.9% | 4.0% |
| Age 21 to 24 | 3.8% | 4.1% | 5.2% |
| Age 25 to 34 | 9.5% | 5.7% | 13.8% |
| Age 35 to 44 | 13.2% | 12.9% | 12.9% |
| Age 45 to 54 | 14.0% | 8.7% | 12.6% |
| Age 55 to 59 | 6.7% | 11.1% | 6.7% |
| Age 60 to 64 | 6.9% | 11.9% | 6.3% |
| Age 65 to 74 | 13.1% | 14.8% | 9.6% |
| Age 75 to 84 | 5.3% | 4.2% | 4.5% |
| Age 85 and over | 2.8% | 1.5% | 1.9% |
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| Race | | | |
| | Salmon Creek, WA | Brush Prairie, WA | United States |
| White | 76.9% | 92.6% | 59.4% |
| Black | 2.1% | 0.0% | 12.2% |
| Asian | 4.5% | 1.6% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.3% | 0.0% | 0.2% |
| Other | 1.1% | 0.0% | 0.4% |
| Two or More Races | 5.8% | 0.0% | 3.2% |
| Hispanic | 9.4% | 5.8% | 18.4% |
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| Marriage & Family | | | |
| | Salmon Creek, WA | Brush Prairie, WA | United States |
| Married Population | 54.7% | 56.1% | 49.8% |
| Currently Married | 53.1% | 55.9% | 48.0% |
| Married but Separated | 1.6% | 0.2% | 1.8% |
| Single Population | 45.3% | 43.9% | 50.2% |
| Never Married | 26.7% | 28.5% | 33.8% |
| Divorced | 11.7% | 9.9% | 10.8% |
| Widowed | 6.9% | 5.5% | 5.6% |
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| Household Size | 2.57 | 2.45 | 2.60 |
| Households | 7,695 | 1,112 | 124,010,992 |
| Family Households | 5,356 | 742 | 80,755,759 |
| Married couple, w/children | 29.7% | 23.5% | 30.5% |
| Married couple, no children | 49.5% | 59.6% | 42.9% |
| Non Family Households | 2,339 | 370 | 43,255,233 |
| Single householder, w/children | 11.4% | 4.4% | 15.8% |
| Single householder, no children | 9.3% | 12.5% | 10.8% |