| | Trenton, MI | Marshall, MI | United States |
| Population | 18,489 | 6,832 | 329,725,481 |
| Female Population | 51.3% | 51.6% | 50.5% |
| Male Population | 48.7% | 48.4% | 49.5% |
| Median Age | 48.9 | 45.4 | 38.4 |
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| Population - 2010 | 18,816 | 7,058 | 309,327,143 |
| Population - 2000 | 19,584 | 7,459 | 285,036,114 |
| Population - 1990 | 20,586 | 6,891 | 251,960,433 |
| Pop. 2000 to Now | -7.9% | -7.2% | 15.6% |
| Pop. 1990 to Now | -12.4% | 0.5% | 30.8% |
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| Population Density | 2,546.3 | 1,074.0 | 93.4 |
| Land Area | 7.3 | 6.4 | 3,531,905.4 |
| Water Area | 0.3 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Trenton, MI | Marshall, MI | United States |
| Age 0 to 4 | 4.5% | 5.3% | 5.9% |
| Age 5 to 9 | 4.8% | 5.4% | 6.1% |
| Age 10 to 14 | 5.6% | 4.7% | 6.6% |
| Age 15 to 17 | 4.6% | 3.4% | 3.9% |
| Age 18 to 20 | 2.7% | 3.0% | 4.0% |
| Age 21 to 24 | 3.8% | 2.9% | 5.2% |
| Age 25 to 34 | 9.1% | 13.6% | 13.8% |
| Age 35 to 44 | 10.4% | 11.3% | 12.9% |
| Age 45 to 54 | 14.5% | 14.3% | 12.6% |
| Age 55 to 59 | 8.1% | 7.5% | 6.7% |
| Age 60 to 64 | 8.9% | 6.4% | 6.3% |
| Age 65 to 74 | 12.8% | 12.9% | 9.6% |
| Age 75 to 84 | 6.8% | 6.4% | 4.5% |
| Age 85 and over | 3.4% | 3.0% | 1.9% |
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| Race | | | |
| | Trenton, MI | Marshall, MI | United States |
| White | 89.0% | 94.3% | 59.4% |
| Black | 2.4% | 0.5% | 12.2% |
| Asian | 0.7% | 0.4% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 3.4% | 1.2% | 3.2% |
| Hispanic | 4.5% | 3.6% | 18.4% |
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| Marriage & Family | | | |
| | Trenton, MI | Marshall, MI | United States |
| Married Population | 52.0% | 48.8% | 49.8% |
| Currently Married | 50.4% | 47.0% | 48.0% |
| Married but Separated | 1.6% | 1.7% | 1.8% |
| Single Population | 48.0% | 51.2% | 50.2% |
| Never Married | 25.3% | 26.7% | 33.8% |
| Divorced | 14.9% | 15.9% | 10.8% |
| Widowed | 7.8% | 8.6% | 5.6% |
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| Household Size | 2.30 | 2.08 | 2.60 |
| Households | 7,913 | 3,236 | 124,010,992 |
| Family Households | 5,024 | 1,770 | 80,755,759 |
| Married couple, w/children | 25.2% | 23.7% | 30.5% |
| Married couple, no children | 49.4% | 52.0% | 42.9% |
| Non Family Households | 2,889 | 1,466 | 43,255,233 |
| Single householder, w/children | 13.6% | 15.7% | 15.8% |
| Single householder, no children | 11.8% | 8.6% | 10.8% |