| | Blackwell, OK | Wellington, KS | United States |
| Population | 6,192 | 7,745 | 329,725,481 |
| Female Population | 47.4% | 47.9% | 50.5% |
| Male Population | 52.6% | 52.1% | 49.5% |
| Median Age | 37.7 | 39.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 7,070 | 8,163 | 309,327,143 |
| Population - 2000 | 7,668 | 8,647 | 285,036,114 |
| Population - 1990 | 7,538 | 8,411 | 251,960,433 |
| Pop. 2000 to Now | -14.9% | -12.7% | 15.6% |
| Pop. 1990 to Now | -13.4% | -10.2% | 30.8% |
| space4 | | | |
| Population Density | 1,110.7 | 1,058.1 | 93.4 |
| Land Area | 5.6 | 7.3 | 3,531,905.4 |
| Water Area | 0.0 | 0.9 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Blackwell, OK | Wellington, KS | United States |
| Age 0 to 4 | 6.7% | 8.2% | 5.9% |
| Age 5 to 9 | 7.6% | 6.5% | 6.1% |
| Age 10 to 14 | 8.0% | 8.4% | 6.6% |
| Age 15 to 17 | 3.3% | 4.3% | 3.9% |
| Age 18 to 20 | 5.8% | 4.0% | 4.0% |
| Age 21 to 24 | 1.9% | 4.9% | 5.2% |
| Age 25 to 34 | 13.0% | 10.1% | 13.8% |
| Age 35 to 44 | 10.1% | 11.5% | 12.9% |
| Age 45 to 54 | 8.1% | 11.3% | 12.6% |
| Age 55 to 59 | 6.4% | 6.9% | 6.7% |
| Age 60 to 64 | 7.5% | 6.5% | 6.3% |
| Age 65 to 74 | 12.5% | 8.0% | 9.6% |
| Age 75 to 84 | 7.7% | 5.6% | 4.5% |
| Age 85 and over | 1.3% | 3.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Blackwell, OK | Wellington, KS | United States |
| White | 70.9% | 81.9% | 59.4% |
| Black | 1.0% | 1.7% | 12.2% |
| Asian | 0.0% | 0.0% | 5.6% |
| Native American | 6.7% | 1.5% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.0% | 0.4% |
| Two or More Races | 8.1% | 4.1% | 3.2% |
| Hispanic | 12.9% | 10.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Blackwell, OK | Wellington, KS | United States |
| Married Population | 49.1% | 45.5% | 49.8% |
| Currently Married | 47.8% | 44.0% | 48.0% |
| Married but Separated | 1.3% | 1.4% | 1.8% |
| Single Population | 50.9% | 54.6% | 50.2% |
| Never Married | 26.7% | 29.4% | 33.8% |
| Divorced | 14.6% | 15.0% | 10.8% |
| Widowed | 9.6% | 10.2% | 5.6% |
| space5 | | | |
| Household Size | 2.61 | 2.60 | 2.60 |
| Households | 2,357 | 2,882 | 124,010,992 |
| Family Households | 1,473 | 1,719 | 80,755,759 |
| Married couple, w/children | 27.2% | 34.3% | 30.5% |
| Married couple, no children | 46.6% | 34.4% | 42.9% |
| Non Family Households | 884 | 1,163 | 43,255,233 |
| Single householder, w/children | 17.9% | 23.3% | 15.8% |
| Single householder, no children | 8.4% | 8.1% | 10.8% |