| | Rainier, WA | Montesano, WA | United States |
| Population | 2,772 | 4,070 | 329,725,481 |
| Female Population | 48.2% | 50.0% | 50.5% |
| Male Population | 51.8% | 50.0% | 49.5% |
| Median Age | 38.2 | 40 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,799 | 3,982 | 309,327,143 |
| Population - 2000 | 1,492 | 3,312 | 285,036,114 |
| Population - 1990 | 991 | 3,064 | 251,960,433 |
| Pop. 2000 to Now | 57.5% | 23.0% | 15.6% |
| Pop. 1990 to Now | 137.1% | 33.0% | 30.8% |
| space4 | | | |
| Population Density | 1,599.5 | 392.8 | 93.4 |
| Land Area | 1.7 | 10.4 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Rainier, WA | Montesano, WA | United States |
| Age 0 to 4 | 6.6% | 5.9% | 5.9% |
| Age 5 to 9 | 8.7% | 7.7% | 6.1% |
| Age 10 to 14 | 7.0% | 6.4% | 6.6% |
| Age 15 to 17 | 3.2% | 5.1% | 3.9% |
| Age 18 to 20 | 1.5% | 3.0% | 4.0% |
| Age 21 to 24 | 1.7% | 2.1% | 5.2% |
| Age 25 to 34 | 16.8% | 16.2% | 13.8% |
| Age 35 to 44 | 14.3% | 8.3% | 12.9% |
| Age 45 to 54 | 12.9% | 10.9% | 12.6% |
| Age 55 to 59 | 6.0% | 4.9% | 6.7% |
| Age 60 to 64 | 8.2% | 4.2% | 6.3% |
| Age 65 to 74 | 9.7% | 11.0% | 9.6% |
| Age 75 to 84 | 3.2% | 11.4% | 4.5% |
| Age 85 and over | 0.1% | 2.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Rainier, WA | Montesano, WA | United States |
| White | 85.6% | 91.4% | 59.4% |
| Black | 0.0% | 0.0% | 12.2% |
| Asian | 1.4% | 1.2% | 5.6% |
| Native American | 0.9% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.5% | 0.0% | 0.4% |
| Two or More Races | 5.2% | 6.0% | 3.2% |
| Hispanic | 6.4% | 1.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Rainier, WA | Montesano, WA | United States |
| Married Population | 50.9% | 52.6% | 49.8% |
| Currently Married | 49.7% | 51.5% | 48.0% |
| Married but Separated | 1.2% | 1.2% | 1.8% |
| Single Population | 49.1% | 47.4% | 50.2% |
| Never Married | 31.2% | 26.0% | 33.8% |
| Divorced | 13.9% | 15.4% | 10.8% |
| Widowed | 4.0% | 5.9% | 5.6% |
| space5 | | | |
| Household Size | 3.08 | 2.50 | 2.60 |
| Households | 900 | 1,577 | 124,010,992 |
| Family Households | 718 | 1,126 | 80,755,759 |
| Married couple, w/children | 20.2% | 26.2% | 30.5% |
| Married couple, no children | 48.1% | 39.8% | 42.9% |
| Non Family Households | 182 | 451 | 43,255,233 |
| Single householder, w/children | 19.4% | 23.2% | 15.8% |
| Single householder, no children | 12.4% | 10.8% | 10.8% |