| | Onaga, KS | Seminole, TX | United States |
| Population | 703 | 6,913 | 329,725,481 |
| Female Population | 51.6% | 47.1% | 50.5% |
| Male Population | 48.4% | 52.9% | 49.5% |
| Median Age | 58.7 | 29.6 | 38.4 |
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| Population - 2010 | 701 | 6,499 | 309,327,143 |
| Population - 2000 | 704 | 5,910 | 285,036,114 |
| Population - 1990 | 761 | 6,342 | 251,960,433 |
| Pop. 2000 to Now | -3.6% | 34.6% | 15.6% |
| Pop. 1990 to Now | -10.8% | 25.4% | 30.8% |
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| Population Density | 1,093.3 | 1,887.3 | 93.4 |
| Land Area | 0.6 | 3.7 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Onaga, KS | Seminole, TX | United States |
| Age 0 to 4 | 2.6% | 10.6% | 5.9% |
| Age 5 to 9 | 3.8% | 8.1% | 6.1% |
| Age 10 to 14 | 5.7% | 8.7% | 6.6% |
| Age 15 to 17 | 2.3% | 3.9% | 3.9% |
| Age 18 to 20 | 0.9% | 2.4% | 4.0% |
| Age 21 to 24 | 1.1% | 6.7% | 5.2% |
| Age 25 to 34 | 7.5% | 16.6% | 13.8% |
| Age 35 to 44 | 11.9% | 15.0% | 12.9% |
| Age 45 to 54 | 7.3% | 7.3% | 12.6% |
| Age 55 to 59 | 9.5% | 4.1% | 6.7% |
| Age 60 to 64 | 5.4% | 5.3% | 6.3% |
| Age 65 to 74 | 20.8% | 5.7% | 9.6% |
| Age 75 to 84 | 11.4% | 4.3% | 4.5% |
| Age 85 and over | 9.8% | 1.2% | 1.9% |
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| Race | | | |
| | Onaga, KS | Seminole, TX | United States |
| White | 96.6% | 41.0% | 59.4% |
| Black | 0.0% | 0.8% | 12.2% |
| Asian | 0.0% | 2.9% | 5.6% |
| Native American | 0.4% | 1.5% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.6% | 0.0% | 3.2% |
| Hispanic | 0.4% | 53.7% | 18.4% |
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| Marriage & Family | | | |
| | Onaga, KS | Seminole, TX | United States |
| Married Population | 50.5% | 62.9% | 49.8% |
| Currently Married | 48.1% | 61.8% | 48.0% |
| Married but Separated | 2.4% | 1.1% | 1.8% |
| Single Population | 49.5% | 37.1% | 50.2% |
| Never Married | 17.8% | 22.6% | 33.8% |
| Divorced | 18.1% | 10.2% | 10.8% |
| Widowed | 13.6% | 4.3% | 5.6% |
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| Household Size | 2.23 | 2.59 | 2.60 |
| Households | 273 | 2,637 | 124,010,992 |
| Family Households | 136 | 1,836 | 80,755,759 |
| Married couple, w/children | 30.1% | 39.7% | 30.5% |
| Married couple, no children | 48.5% | 44.1% | 42.9% |
| Non Family Households | 137 | 801 | 43,255,233 |
| Single householder, w/children | 8.1% | 10.9% | 15.8% |
| Single householder, no children | 13.2% | 5.3% | 10.8% |