| | Jefferson, SC | Harvard, IL | United States |
| Population | 896 | 9,482 | 329,725,481 |
| Female Population | 58.7% | 51.3% | 50.5% |
| Male Population | 41.3% | 48.7% | 49.5% |
| Median Age | 32.5 | 28.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 730 | 9,436 | 309,327,143 |
| Population - 2000 | 704 | 7,996 | 285,036,114 |
| Population - 1990 | 745 | 5,975 | 251,960,433 |
| Pop. 2000 to Now | 0.0% | 12.3% | 15.6% |
| Pop. 1990 to Now | -5.5% | 50.3% | 30.8% |
| space4 | | | |
| Population Density | 497.2 | 1,163.6 | 93.4 |
| Land Area | 1.8 | 8.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Jefferson, SC | Harvard, IL | United States |
| Age 0 to 4 | 8.6% | 7.1% | 5.9% |
| Age 5 to 9 | 9.8% | 9.3% | 6.1% |
| Age 10 to 14 | 7.6% | 12.3% | 6.6% |
| Age 15 to 17 | 3.0% | 5.9% | 3.9% |
| Age 18 to 20 | 2.7% | 4.3% | 4.0% |
| Age 21 to 24 | 4.9% | 5.1% | 5.2% |
| Age 25 to 34 | 16.9% | 15.9% | 13.8% |
| Age 35 to 44 | 5.5% | 11.1% | 12.9% |
| Age 45 to 54 | 11.4% | 11.2% | 12.6% |
| Age 55 to 59 | 5.0% | 5.1% | 6.7% |
| Age 60 to 64 | 5.0% | 4.1% | 6.3% |
| Age 65 to 74 | 10.4% | 6.3% | 9.6% |
| Age 75 to 84 | 9.0% | 1.9% | 4.5% |
| Age 85 and over | 0.2% | 0.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Jefferson, SC | Harvard, IL | United States |
| White | 59.5% | 43.4% | 59.4% |
| Black | 36.3% | 0.4% | 12.2% |
| Asian | 0.0% | 0.2% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 3.5% | 1.7% | 3.2% |
| Hispanic | 0.8% | 54.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Jefferson, SC | Harvard, IL | United States |
| Married Population | 50.7% | 46.4% | 49.8% |
| Currently Married | 47.2% | 44.7% | 48.0% |
| Married but Separated | 3.5% | 1.7% | 1.8% |
| Single Population | 49.3% | 53.6% | 50.2% |
| Never Married | 30.0% | 39.3% | 33.8% |
| Divorced | 7.5% | 10.5% | 10.8% |
| Widowed | 11.8% | 3.8% | 5.6% |
| space5 | | | |
| Household Size | 2.62 | 3.22 | 2.60 |
| Households | 336 | 2,946 | 124,010,992 |
| Family Households | 256 | 2,158 | 80,755,759 |
| Married couple, w/children | 15.6% | 39.0% | 30.5% |
| Married couple, no children | 35.5% | 24.7% | 42.9% |
| Non Family Households | 80 | 788 | 43,255,233 |
| Single householder, w/children | 36.7% | 24.3% | 15.8% |
| Single householder, no children | 12.1% | 12.0% | 10.8% |