| | Salem, IL | Fairfield, IL | United States |
| Population | 7,269 | 4,982 | 329,725,481 |
| Female Population | 54.1% | 50.2% | 50.5% |
| Male Population | 45.9% | 49.8% | 49.5% |
| Median Age | 36.8 | 42.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 7,451 | 5,160 | 309,327,143 |
| Population - 2000 | 7,909 | 5,421 | 285,036,114 |
| Population - 1990 | 7,470 | 5,439 | 251,960,433 |
| Pop. 2000 to Now | -12.1% | -9.8% | 15.6% |
| Pop. 1990 to Now | -6.9% | -10.1% | 30.8% |
| space4 | | | |
| Population Density | 1,046.5 | 1,237.2 | 93.4 |
| Land Area | 6.9 | 4.0 | 3,531,905.4 |
| Water Area | 0.2 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Salem, IL | Fairfield, IL | United States |
| Age 0 to 4 | 6.5% | 6.9% | 5.9% |
| Age 5 to 9 | 6.6% | 5.3% | 6.1% |
| Age 10 to 14 | 6.2% | 5.7% | 6.6% |
| Age 15 to 17 | 5.1% | 3.3% | 3.9% |
| Age 18 to 20 | 2.4% | 4.6% | 4.0% |
| Age 21 to 24 | 4.5% | 4.8% | 5.2% |
| Age 25 to 34 | 16.3% | 11.9% | 13.8% |
| Age 35 to 44 | 12.0% | 11.8% | 12.9% |
| Age 45 to 54 | 11.0% | 11.0% | 12.6% |
| Age 55 to 59 | 5.0% | 8.7% | 6.7% |
| Age 60 to 64 | 6.0% | 5.5% | 6.3% |
| Age 65 to 74 | 9.6% | 9.8% | 9.6% |
| Age 75 to 84 | 5.8% | 6.5% | 4.5% |
| Age 85 and over | 2.8% | 4.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Salem, IL | Fairfield, IL | United States |
| White | 92.8% | 93.8% | 59.4% |
| Black | 3.6% | 3.1% | 12.2% |
| Asian | 0.4% | 0.6% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.7% | 1.0% | 3.2% |
| Hispanic | 0.4% | 1.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Salem, IL | Fairfield, IL | United States |
| Married Population | 45.1% | 47.6% | 49.8% |
| Currently Married | 41.5% | 47.3% | 48.0% |
| Married but Separated | 3.7% | 0.3% | 1.8% |
| Single Population | 54.9% | 52.4% | 50.2% |
| Never Married | 35.5% | 24.2% | 33.8% |
| Divorced | 11.2% | 17.1% | 10.8% |
| Widowed | 8.2% | 11.1% | 5.6% |
| space5 | | | |
| Household Size | 2.37 | 2.12 | 2.60 |
| Households | 2,980 | 2,333 | 124,010,992 |
| Family Households | 1,849 | 1,385 | 80,755,759 |
| Married couple, w/children | 24.2% | 30.7% | 30.5% |
| Married couple, no children | 40.1% | 40.1% | 42.9% |
| Non Family Households | 1,131 | 948 | 43,255,233 |
| Single householder, w/children | 30.3% | 21.5% | 15.8% |
| Single householder, no children | 5.4% | 7.7% | 10.8% |