| | Jacksonville, NC | Rock Island, IL | United States |
| Population | 73,224 | 37,519 | 329,725,481 |
| Female Population | 38.5% | 50.0% | 50.5% |
| Male Population | 61.5% | 50.0% | 49.5% |
| Median Age | 23.2 | 35.4 | 38.4 |
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| Population - 2010 | 78,056 | 38,973 | 309,327,143 |
| Population - 2000 | 66,715 | 39,684 | 285,036,114 |
| Population - 1990 | 30,013 | 40,552 | 251,960,433 |
| Pop. 2000 to Now | 14.3% | -7.1% | 15.6% |
| Pop. 1990 to Now | 154.2% | -9.1% | 30.8% |
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| Population Density | 1,508.1 | 2,226.0 | 93.4 |
| Land Area | 48.6 | 16.9 | 3,531,905.4 |
| Water Area | 7.6 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Jacksonville, NC | Rock Island, IL | United States |
| Age 0 to 4 | 8.1% | 6.2% | 5.9% |
| Age 5 to 9 | 5.5% | 5.3% | 6.1% |
| Age 10 to 14 | 4.6% | 6.9% | 6.6% |
| Age 15 to 17 | 2.3% | 3.9% | 3.9% |
| Age 18 to 20 | 15.3% | 8.5% | 4.0% |
| Age 21 to 24 | 22.4% | 5.9% | 5.2% |
| Age 25 to 34 | 17.0% | 12.8% | 13.8% |
| Age 35 to 44 | 7.8% | 11.4% | 12.9% |
| Age 45 to 54 | 5.0% | 9.9% | 12.6% |
| Age 55 to 59 | 3.0% | 5.7% | 6.7% |
| Age 60 to 64 | 2.8% | 6.3% | 6.3% |
| Age 65 to 74 | 4.1% | 10.0% | 9.6% |
| Age 75 to 84 | 1.4% | 4.5% | 4.5% |
| Age 85 and over | 0.7% | 2.5% | 1.9% |
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| Race | | | |
| | Jacksonville, NC | Rock Island, IL | United States |
| White | 54.2% | 61.1% | 59.4% |
| Black | 17.6% | 17.1% | 12.2% |
| Asian | 3.0% | 4.5% | 5.6% |
| Native American | 0.2% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.1% | 0.2% |
| Other | 0.1% | 0.1% | 0.4% |
| Two or More Races | 5.7% | 3.2% | 3.2% |
| Hispanic | 19.1% | 13.7% | 18.4% |
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| Marriage & Family | | | |
| | Jacksonville, NC | Rock Island, IL | United States |
| Married Population | 44.7% | 39.4% | 49.8% |
| Currently Married | 42.1% | 37.6% | 48.0% |
| Married but Separated | 2.6% | 1.8% | 1.8% |
| Single Population | 55.3% | 60.6% | 50.2% |
| Never Married | 45.2% | 41.2% | 33.8% |
| Divorced | 7.6% | 12.6% | 10.8% |
| Widowed | 2.6% | 6.7% | 5.6% |
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| Household Size | 2.50 | 2.26 | 2.60 |
| Households | 21,614 | 15,285 | 124,010,992 |
| Family Households | 15,321 | 7,918 | 80,755,759 |
| Married couple, w/children | 35.0% | 27.4% | 30.5% |
| Married couple, no children | 40.0% | 39.9% | 42.9% |
| Non Family Households | 6,293 | 7,367 | 43,255,233 |
| Single householder, w/children | 17.3% | 21.8% | 15.8% |
| Single householder, no children | 7.6% | 10.8% | 10.8% |