| | Florence, SC | Summerville, SC | United States |
| Population | 39,816 | 50,318 | 329,725,481 |
| Female Population | 54.9% | 51.6% | 50.5% |
| Male Population | 45.1% | 48.4% | 49.5% |
| Median Age | 39.2 | 38.3 | 38.4 |
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| Population - 2010 | 37,928 | 43,181 | 309,327,143 |
| Population - 2000 | 30,248 | 27,752 | 285,036,114 |
| Population - 1990 | 29,813 | 22,519 | 251,960,433 |
| Pop. 2000 to Now | 27.2% | 92.1% | 15.6% |
| Pop. 1990 to Now | 29.0% | 136.7% | 30.8% |
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| Population Density | 1,789.4 | 2,575.9 | 93.4 |
| Land Area | 22.3 | 19.5 | 3,531,905.4 |
| Water Area | 0.1 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Florence, SC | Summerville, SC | United States |
| Age 0 to 4 | 6.5% | 6.4% | 5.9% |
| Age 5 to 9 | 6.2% | 6.9% | 6.1% |
| Age 10 to 14 | 7.7% | 6.7% | 6.6% |
| Age 15 to 17 | 4.1% | 3.6% | 3.9% |
| Age 18 to 20 | 2.8% | 2.7% | 4.0% |
| Age 21 to 24 | 3.8% | 5.5% | 5.2% |
| Age 25 to 34 | 13.9% | 13.0% | 13.8% |
| Age 35 to 44 | 12.5% | 14.4% | 12.9% |
| Age 45 to 54 | 11.9% | 11.8% | 12.6% |
| Age 55 to 59 | 6.2% | 6.8% | 6.7% |
| Age 60 to 64 | 5.8% | 7.9% | 6.3% |
| Age 65 to 74 | 11.7% | 8.9% | 9.6% |
| Age 75 to 84 | 5.3% | 3.7% | 4.5% |
| Age 85 and over | 1.8% | 1.6% | 1.9% |
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| Race | | | |
| | Florence, SC | Summerville, SC | United States |
| White | 45.8% | 69.0% | 59.4% |
| Black | 47.4% | 19.2% | 12.2% |
| Asian | 2.6% | 2.1% | 5.6% |
| Native American | 0.4% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.5% | 0.5% | 0.4% |
| Two or More Races | 1.2% | 2.9% | 3.2% |
| Hispanic | 2.0% | 6.1% | 18.4% |
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| Marriage & Family | | | |
| | Florence, SC | Summerville, SC | United States |
| Married Population | 47.9% | 53.3% | 49.8% |
| Currently Married | 44.7% | 50.7% | 48.0% |
| Married but Separated | 3.2% | 2.6% | 1.8% |
| Single Population | 52.1% | 46.7% | 50.2% |
| Never Married | 34.4% | 28.4% | 33.8% |
| Divorced | 10.9% | 11.0% | 10.8% |
| Widowed | 6.7% | 7.4% | 5.6% |
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| Household Size | 2.39 | 2.55 | 2.60 |
| Households | 16,412 | 19,616 | 124,010,992 |
| Family Households | 9,928 | 13,033 | 80,755,759 |
| Married couple, w/children | 27.9% | 30.3% | 30.5% |
| Married couple, no children | 38.8% | 44.1% | 42.9% |
| Non Family Households | 6,484 | 6,583 | 43,255,233 |
| Single householder, w/children | 22.0% | 16.2% | 15.8% |
| Single householder, no children | 11.2% | 9.3% | 10.8% |