| | St. Helens, OR | Longview, WA | United States |
| Population | 13,808 | 37,542 | 329,725,481 |
| Female Population | 51.0% | 52.4% | 50.5% |
| Male Population | 49.0% | 47.6% | 49.5% |
| Median Age | 36.6 | 38.8 | 38.4 |
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| Population - 2010 | 13,050 | 36,794 | 309,327,143 |
| Population - 2000 | 10,019 | 34,660 | 285,036,114 |
| Population - 1990 | 7,535 | 31,499 | 251,960,433 |
| Pop. 2000 to Now | 40.4% | 11.1% | 15.6% |
| Pop. 1990 to Now | 86.7% | 22.3% | 30.8% |
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| Population Density | 2,885.7 | 2,525.0 | 93.4 |
| Land Area | 4.8 | 14.9 | 3,531,905.4 |
| Water Area | 1.1 | 0.5 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | St. Helens, OR | Longview, WA | United States |
| Age 0 to 4 | 7.7% | 5.9% | 5.9% |
| Age 5 to 9 | 6.0% | 5.4% | 6.1% |
| Age 10 to 14 | 5.0% | 6.8% | 6.6% |
| Age 15 to 17 | 4.7% | 3.9% | 3.9% |
| Age 18 to 20 | 3.0% | 3.7% | 4.0% |
| Age 21 to 24 | 4.7% | 4.6% | 5.2% |
| Age 25 to 34 | 16.4% | 13.8% | 13.8% |
| Age 35 to 44 | 11.8% | 12.3% | 12.9% |
| Age 45 to 54 | 12.6% | 10.5% | 12.6% |
| Age 55 to 59 | 7.9% | 5.9% | 6.7% |
| Age 60 to 64 | 7.3% | 6.2% | 6.3% |
| Age 65 to 74 | 8.1% | 11.7% | 9.6% |
| Age 75 to 84 | 2.7% | 6.0% | 4.5% |
| Age 85 and over | 1.9% | 3.1% | 1.9% |
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| Race | | | |
| | St. Helens, OR | Longview, WA | United States |
| White | 84.4% | 79.0% | 59.4% |
| Black | 0.5% | 1.3% | 12.2% |
| Asian | 0.6% | 1.7% | 5.6% |
| Native American | 0.3% | 1.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.2% | 0.2% |
| Other | 0.6% | 0.0% | 0.4% |
| Two or More Races | 6.0% | 6.1% | 3.2% |
| Hispanic | 7.4% | 10.4% | 18.4% |
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| Marriage & Family | | | |
| | St. Helens, OR | Longview, WA | United States |
| Married Population | 42.1% | 44.0% | 49.8% |
| Currently Married | 41.2% | 41.2% | 48.0% |
| Married but Separated | 0.9% | 2.7% | 1.8% |
| Single Population | 57.9% | 56.0% | 50.2% |
| Never Married | 33.0% | 31.8% | 33.8% |
| Divorced | 18.2% | 16.1% | 10.8% |
| Widowed | 6.7% | 8.1% | 5.6% |
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| Household Size | 2.66 | 2.30 | 2.60 |
| Households | 5,060 | 15,913 | 124,010,992 |
| Family Households | 3,428 | 8,847 | 80,755,759 |
| Married couple, w/children | 27.5% | 25.2% | 30.5% |
| Married couple, no children | 35.6% | 40.9% | 42.9% |
| Non Family Households | 1,632 | 7,066 | 43,255,233 |
| Single householder, w/children | 24.8% | 22.1% | 15.8% |
| Single householder, no children | 12.2% | 11.8% | 10.8% |