| | St. Joseph, TN | Jackson, TN | United States |
| Population | 800 | 67,753 | 329,725,481 |
| Female Population | 48.8% | 53.3% | 50.5% |
| Male Population | 51.3% | 46.7% | 49.5% |
| Median Age | 40.4 | 34.5 | 38.4 |
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| Population - 2010 | 791 | 66,813 | 309,327,143 |
| Population - 2000 | 829 | 59,643 | 285,036,114 |
| Population - 1990 | 789 | 48,949 | 251,960,433 |
| Pop. 2000 to Now | -0.6% | 13.0% | 15.6% |
| Pop. 1990 to Now | 4.4% | 37.7% | 30.8% |
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| Population Density | 212.4 | 1,162.5 | 93.4 |
| Land Area | 3.8 | 58.3 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | St. Joseph, TN | Jackson, TN | United States |
| Age 0 to 4 | 6.3% | 7.1% | 5.9% |
| Age 5 to 9 | 7.4% | 6.8% | 6.1% |
| Age 10 to 14 | 4.4% | 7.3% | 6.6% |
| Age 15 to 17 | 1.8% | 4.0% | 3.9% |
| Age 18 to 20 | 2.8% | 6.2% | 4.0% |
| Age 21 to 24 | 2.9% | 5.7% | 5.2% |
| Age 25 to 34 | 18.4% | 13.7% | 13.8% |
| Age 35 to 44 | 9.1% | 11.8% | 12.9% |
| Age 45 to 54 | 14.9% | 10.4% | 12.6% |
| Age 55 to 59 | 9.1% | 6.0% | 6.7% |
| Age 60 to 64 | 4.5% | 6.2% | 6.3% |
| Age 65 to 74 | 10.1% | 8.8% | 9.6% |
| Age 75 to 84 | 7.5% | 4.2% | 4.5% |
| Age 85 and over | 1.0% | 1.8% | 1.9% |
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| Race | | | |
| | St. Joseph, TN | Jackson, TN | United States |
| White | 97.8% | 45.5% | 59.4% |
| Black | 0.0% | 45.7% | 12.2% |
| Asian | 1.5% | 1.3% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.7% | 0.4% |
| Two or More Races | 0.4% | 2.5% | 3.2% |
| Hispanic | 0.4% | 4.3% | 18.4% |
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| Marriage & Family | | | |
| | St. Joseph, TN | Jackson, TN | United States |
| Married Population | 47.4% | 39.3% | 49.8% |
| Currently Married | 45.3% | 36.4% | 48.0% |
| Married but Separated | 2.1% | 3.0% | 1.8% |
| Single Population | 52.6% | 60.7% | 50.2% |
| Never Married | 24.2% | 40.4% | 33.8% |
| Divorced | 18.8% | 13.5% | 10.8% |
| Widowed | 9.6% | 6.8% | 5.6% |
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| Household Size | 2.39 | 2.46 | 2.60 |
| Households | 335 | 26,083 | 124,010,992 |
| Family Households | 189 | 15,351 | 80,755,759 |
| Married couple, w/children | 37.0% | 22.8% | 30.5% |
| Married couple, no children | 33.3% | 33.9% | 42.9% |
| Non Family Households | 146 | 10,732 | 43,255,233 |
| Single householder, w/children | 12.7% | 30.5% | 15.8% |
| Single householder, no children | 16.9% | 12.8% | 10.8% |