| | Louisville, TN | Gallatin, TN | United States |
| Population | 4,337 | 43,306 | 329,725,481 |
| Female Population | 50.4% | 50.1% | 50.5% |
| Male Population | 49.6% | 49.9% | 49.5% |
| Median Age | 51.9 | 38.2 | 38.4 |
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| Population - 2010 | 4,067 | 30,514 | 309,327,143 |
| Population - 2000 | 2,001 | 23,230 | 285,036,114 |
| Population - 1990 | 1,893 | 18,794 | 251,960,433 |
| Pop. 2000 to Now | 106.9% | 90.9% | 15.6% |
| Pop. 1990 to Now | 118.7% | 135.9% | 30.8% |
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| Population Density | 290.7 | 1,363.0 | 93.4 |
| Land Area | 14.9 | 31.8 | 3,531,905.4 |
| Water Area | 2.1 | 0.6 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Louisville, TN | Gallatin, TN | United States |
| Age 0 to 4 | 3.8% | 5.8% | 5.9% |
| Age 5 to 9 | 2.4% | 8.0% | 6.1% |
| Age 10 to 14 | 3.2% | 6.0% | 6.6% |
| Age 15 to 17 | 2.5% | 2.9% | 3.9% |
| Age 18 to 20 | 4.0% | 3.7% | 4.0% |
| Age 21 to 24 | 2.4% | 4.4% | 5.2% |
| Age 25 to 34 | 10.7% | 14.5% | 13.8% |
| Age 35 to 44 | 10.5% | 13.1% | 12.9% |
| Age 45 to 54 | 17.2% | 13.6% | 12.6% |
| Age 55 to 59 | 7.7% | 6.5% | 6.7% |
| Age 60 to 64 | 9.9% | 5.3% | 6.3% |
| Age 65 to 74 | 19.4% | 9.0% | 9.6% |
| Age 75 to 84 | 4.9% | 5.5% | 4.5% |
| Age 85 and over | 1.3% | 1.7% | 1.9% |
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| Race | | | |
| | Louisville, TN | Gallatin, TN | United States |
| White | 91.0% | 69.9% | 59.4% |
| Black | 4.2% | 13.9% | 12.2% |
| Asian | 1.3% | 2.8% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 1.3% | 4.6% | 3.2% |
| Hispanic | 2.2% | 8.3% | 18.4% |
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| Marriage & Family | | | |
| | Louisville, TN | Gallatin, TN | United States |
| Married Population | 64.1% | 52.0% | 49.8% |
| Currently Married | 63.0% | 51.2% | 48.0% |
| Married but Separated | 1.2% | 0.8% | 1.8% |
| Single Population | 35.9% | 48.0% | 50.2% |
| Never Married | 20.0% | 29.0% | 33.8% |
| Divorced | 9.7% | 13.0% | 10.8% |
| Widowed | 6.2% | 6.0% | 5.6% |
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| Household Size | 2.30 | 2.47 | 2.60 |
| Households | 1,872 | 17,127 | 124,010,992 |
| Family Households | 1,418 | 11,622 | 80,755,759 |
| Married couple, w/children | 18.1% | 26.9% | 30.5% |
| Married couple, no children | 66.9% | 45.1% | 42.9% |
| Non Family Households | 454 | 5,505 | 43,255,233 |
| Single householder, w/children | 6.2% | 17.7% | 15.8% |
| Single householder, no children | 8.9% | 10.2% | 10.8% |