| | Ellensburg, WA | Wilmington, DE | United States |
| Population | 19,215 | 70,926 | 329,725,481 |
| Female Population | 49.7% | 52.9% | 50.5% |
| Male Population | 50.3% | 47.1% | 49.5% |
| Median Age | 24.4 | 36.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 18,332 | 70,834 | 309,327,143 |
| Population - 2000 | 15,414 | 72,664 | 285,036,114 |
| Population - 1990 | 12,361 | 71,529 | 251,960,433 |
| Pop. 2000 to Now | 40.0% | -3.2% | 15.6% |
| Pop. 1990 to Now | 74.6% | -1.6% | 30.8% |
| space4 | | | |
| Population Density | 2,503.3 | 6,504.6 | 93.4 |
| Land Area | 7.7 | 10.9 | 3,531,905.4 |
| Water Area | 0.1 | 6.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Ellensburg, WA | Wilmington, DE | United States |
| Age 0 to 4 | 4.4% | 5.9% | 5.9% |
| Age 5 to 9 | 3.7% | 5.7% | 6.1% |
| Age 10 to 14 | 3.3% | 7.0% | 6.6% |
| Age 15 to 17 | 2.1% | 3.5% | 3.9% |
| Age 18 to 20 | 20.1% | 3.3% | 4.0% |
| Age 21 to 24 | 18.6% | 4.7% | 5.2% |
| Age 25 to 34 | 14.6% | 18.0% | 13.8% |
| Age 35 to 44 | 8.4% | 13.1% | 12.9% |
| Age 45 to 54 | 8.0% | 11.7% | 12.6% |
| Age 55 to 59 | 3.6% | 6.4% | 6.7% |
| Age 60 to 64 | 3.6% | 7.1% | 6.3% |
| Age 65 to 74 | 5.2% | 8.3% | 9.6% |
| Age 75 to 84 | 3.1% | 3.8% | 4.5% |
| Age 85 and over | 1.4% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Ellensburg, WA | Wilmington, DE | United States |
| White | 78.1% | 28.9% | 59.4% |
| Black | 1.9% | 56.1% | 12.2% |
| Asian | 2.2% | 1.2% | 5.6% |
| Native American | 0.4% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.8% | 0.0% | 0.2% |
| Other | 0.0% | 0.5% | 0.4% |
| Two or More Races | 6.7% | 2.6% | 3.2% |
| Hispanic | 10.0% | 10.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Ellensburg, WA | Wilmington, DE | United States |
| Married Population | 28.6% | 29.2% | 49.8% |
| Currently Married | 27.7% | 26.7% | 48.0% |
| Married but Separated | 1.0% | 2.5% | 1.8% |
| Single Population | 71.4% | 70.8% | 50.2% |
| Never Married | 58.1% | 52.5% | 33.8% |
| Divorced | 10.0% | 12.8% | 10.8% |
| Widowed | 3.3% | 5.6% | 5.6% |
| space5 | | | |
| Household Size | 2.04 | 2.16 | 2.60 |
| Households | 8,235 | 31,392 | 124,010,992 |
| Family Households | 3,364 | 14,282 | 80,755,759 |
| Married couple, w/children | 26.1% | 16.2% | 30.5% |
| Married couple, no children | 39.6% | 29.7% | 42.9% |
| Non Family Households | 4,871 | 17,110 | 43,255,233 |
| Single householder, w/children | 18.8% | 32.7% | 15.8% |
| Single householder, no children | 15.5% | 21.3% | 10.8% |