| | Union, WA | Cathlamet, WA | United States |
| Population | 307 | 599 | 329,725,481 |
| Female Population | 53.1% | 58.1% | 50.5% |
| Male Population | 46.9% | 41.9% | 49.5% |
| Median Age | 53.5 | 54.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 526 | 533 | 309,327,143 |
| Population - 2000 | 513 | 565 | 285,036,114 |
| Population - 1990 | 416 | 508 | 251,960,433 |
| Pop. 2000 to Now | -40.7% | -4.3% | 15.6% |
| Pop. 1990 to Now | -26.9% | 6.5% | 30.8% |
| space4 | | | |
| Population Density | 189.9 | 1,200.4 | 93.4 |
| Land Area | 1.6 | 0.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Union, WA | Cathlamet, WA | United States |
| Age 0 to 4 | 0.0% | 9.5% | 5.9% |
| Age 5 to 9 | 0.0% | 2.5% | 6.1% |
| Age 10 to 14 | 6.5% | 1.5% | 6.6% |
| Age 15 to 17 | 7.8% | 1.3% | 3.9% |
| Age 18 to 20 | 0.0% | 3.0% | 4.0% |
| Age 21 to 24 | 0.0% | 4.5% | 5.2% |
| Age 25 to 34 | 0.0% | 9.7% | 13.8% |
| Age 35 to 44 | 5.5% | 7.0% | 12.9% |
| Age 45 to 54 | 32.2% | 11.4% | 12.6% |
| Age 55 to 59 | 5.5% | 9.7% | 6.7% |
| Age 60 to 64 | 9.4% | 6.8% | 6.3% |
| Age 65 to 74 | 27.4% | 24.4% | 9.6% |
| Age 75 to 84 | 5.5% | 4.7% | 4.5% |
| Age 85 and over | 0.0% | 4.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Union, WA | Cathlamet, WA | United States |
| White | 74.9% | 95.3% | 59.4% |
| Black | 0.0% | 1.0% | 12.2% |
| Asian | 0.0% | 0.2% | 5.6% |
| Native American | 0.0% | 0.8% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 25.1% | 0.8% | 3.2% |
| Hispanic | 0.0% | 1.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Union, WA | Cathlamet, WA | United States |
| Married Population | 65.9% | 53.5% | 49.8% |
| Currently Married | 65.9% | 48.1% | 48.0% |
| Married but Separated | 0.0% | 5.4% | 1.8% |
| Single Population | 34.1% | 46.5% | 50.2% |
| Never Married | 18.1% | 20.1% | 33.8% |
| Divorced | 0.0% | 18.3% | 10.8% |
| Widowed | 16.0% | 8.1% | 5.6% |
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| Household Size | 2.06 | 2.06 | 2.60 |
| Households | 149 | 272 | 124,010,992 |
| Family Households | 75 | 163 | 80,755,759 |
| Married couple, w/children | 29.3% | 21.5% | 30.5% |
| Married couple, no children | 70.7% | 55.2% | 42.9% |
| Non Family Households | 74 | 109 | 43,255,233 |
| Single householder, w/children | 0.0% | 14.1% | 15.8% |
| Single householder, no children | 0.0% | 9.2% | 10.8% |