| | Arlington, TX | Trinidad, CO | United States |
| Population | 392,304 | 8,318 | 329,725,481 |
| Female Population | 51.0% | 47.2% | 50.5% |
| Male Population | 49.0% | 52.9% | 49.5% |
| Median Age | 33.1 | 43.1 | 38.4 |
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| Population - 2010 | 365,920 | 9,011 | 309,327,143 |
| Population - 2000 | 332,969 | 9,078 | 285,036,114 |
| Population - 1990 | 261,721 | 8,580 | 251,960,433 |
| Pop. 2000 to Now | 19.8% | -10.5% | 15.6% |
| Pop. 1990 to Now | 52.4% | -5.3% | 30.8% |
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| Population Density | 4,094.6 | 886.2 | 93.4 |
| Land Area | 95.8 | 9.4 | 3,531,905.4 |
| Water Area | 3.7 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Arlington, TX | Trinidad, CO | United States |
| Age 0 to 4 | 6.7% | 4.5% | 5.9% |
| Age 5 to 9 | 7.3% | 5.2% | 6.1% |
| Age 10 to 14 | 7.4% | 5.0% | 6.6% |
| Age 15 to 17 | 4.5% | 4.4% | 3.9% |
| Age 18 to 20 | 4.9% | 4.0% | 4.0% |
| Age 21 to 24 | 6.2% | 4.7% | 5.2% |
| Age 25 to 34 | 15.9% | 12.9% | 13.8% |
| Age 35 to 44 | 13.1% | 12.4% | 12.9% |
| Age 45 to 54 | 12.6% | 11.8% | 12.6% |
| Age 55 to 59 | 5.7% | 8.1% | 6.7% |
| Age 60 to 64 | 5.2% | 6.5% | 6.3% |
| Age 65 to 74 | 7.0% | 12.6% | 9.6% |
| Age 75 to 84 | 2.7% | 5.3% | 4.5% |
| Age 85 and over | 1.0% | 2.6% | 1.9% |
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| Race | | | |
| | Arlington, TX | Trinidad, CO | United States |
| White | 37.6% | 46.3% | 59.4% |
| Black | 22.4% | 0.2% | 12.2% |
| Asian | 6.6% | 1.0% | 5.6% |
| Native American | 0.2% | 0.5% | 0.6% |
| Hawaiian, Pacific Islander | 0.3% | 0.0% | 0.2% |
| Other | 0.4% | 0.7% | 0.4% |
| Two or More Races | 2.7% | 4.6% | 3.2% |
| Hispanic | 29.9% | 46.8% | 18.4% |
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| Marriage & Family | | | |
| | Arlington, TX | Trinidad, CO | United States |
| Married Population | 48.3% | 41.2% | 49.8% |
| Currently Married | 45.9% | 38.9% | 48.0% |
| Married but Separated | 2.3% | 2.3% | 1.8% |
| Single Population | 51.7% | 58.8% | 50.2% |
| Never Married | 36.4% | 34.7% | 33.8% |
| Divorced | 11.0% | 16.7% | 10.8% |
| Widowed | 4.4% | 7.5% | 5.6% |
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| Household Size | 2.85 | 2.12 | 2.60 |
| Households | 136,263 | 3,756 | 124,010,992 |
| Family Households | 93,680 | 2,028 | 80,755,759 |
| Married couple, w/children | 32.7% | 19.1% | 30.5% |
| Married couple, no children | 35.8% | 44.6% | 42.9% |
| Non Family Households | 42,583 | 1,728 | 43,255,233 |
| Single householder, w/children | 19.4% | 25.8% | 15.8% |
| Single householder, no children | 12.1% | 10.5% | 10.8% |