| | Franklin, WI | South Milwaukee, WI | United States |
| Population | 36,685 | 20,785 | 329,725,481 |
| Female Population | 49.7% | 50.7% | 50.5% |
| Male Population | 50.3% | 49.3% | 49.5% |
| Median Age | 43.5 | 41.1 | 38.4 |
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| Population - 2010 | 35,499 | 21,163 | 309,327,143 |
| Population - 2000 | 29,494 | 21,256 | 285,036,114 |
| Population - 1990 | 21,855 | 20,958 | 251,960,433 |
| Pop. 2000 to Now | 21.8% | -2.7% | 15.6% |
| Pop. 1990 to Now | 64.4% | -1.4% | 30.8% |
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| Population Density | 1,061.0 | 4,304.2 | 93.4 |
| Land Area | 34.6 | 4.8 | 3,531,905.4 |
| Water Area | 0.1 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Franklin, WI | South Milwaukee, WI | United States |
| Age 0 to 4 | 5.4% | 6.7% | 5.9% |
| Age 5 to 9 | 5.6% | 5.3% | 6.1% |
| Age 10 to 14 | 6.1% | 5.6% | 6.6% |
| Age 15 to 17 | 3.6% | 3.7% | 3.9% |
| Age 18 to 20 | 2.8% | 2.6% | 4.0% |
| Age 21 to 24 | 3.8% | 3.0% | 5.2% |
| Age 25 to 34 | 10.2% | 14.2% | 13.8% |
| Age 35 to 44 | 15.1% | 12.4% | 12.9% |
| Age 45 to 54 | 13.2% | 12.8% | 12.6% |
| Age 55 to 59 | 8.1% | 8.1% | 6.7% |
| Age 60 to 64 | 7.8% | 8.0% | 6.3% |
| Age 65 to 74 | 10.1% | 9.7% | 9.6% |
| Age 75 to 84 | 6.1% | 5.0% | 4.5% |
| Age 85 and over | 2.1% | 2.9% | 1.9% |
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| Race | | | |
| | Franklin, WI | South Milwaukee, WI | United States |
| White | 78.5% | 80.3% | 59.4% |
| Black | 5.2% | 2.5% | 12.2% |
| Asian | 5.5% | 0.4% | 5.6% |
| Native American | 0.4% | 0.7% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.5% | 0.0% | 0.4% |
| Two or More Races | 2.6% | 3.4% | 3.2% |
| Hispanic | 6.3% | 12.6% | 18.4% |
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| Marriage & Family | | | |
| | Franklin, WI | South Milwaukee, WI | United States |
| Married Population | 58.7% | 48.4% | 49.8% |
| Currently Married | 58.3% | 47.6% | 48.0% |
| Married but Separated | 0.5% | 0.8% | 1.8% |
| Single Population | 41.3% | 51.6% | 50.2% |
| Never Married | 27.5% | 32.5% | 33.8% |
| Divorced | 7.9% | 12.2% | 10.8% |
| Widowed | 5.9% | 6.9% | 5.6% |
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| Household Size | 2.47 | 2.38 | 2.60 |
| Households | 14,015 | 8,612 | 124,010,992 |
| Family Households | 9,635 | 5,308 | 80,755,759 |
| Married couple, w/children | 31.6% | 25.9% | 30.5% |
| Married couple, no children | 55.6% | 45.7% | 42.9% |
| Non Family Households | 4,380 | 3,304 | 43,255,233 |
| Single householder, w/children | 7.9% | 17.0% | 15.8% |
| Single householder, no children | 4.9% | 11.3% | 10.8% |