| | Vandalia, IL | Greenville, IL | United States |
| Population | 6,459 | 6,676 | 329,725,481 |
| Female Population | 39.8% | 40.1% | 50.5% |
| Male Population | 60.2% | 59.9% | 49.5% |
| Median Age | 41.7 | 38.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 7,038 | 7,075 | 309,327,143 |
| Population - 2000 | 6,975 | 6,955 | 285,036,114 |
| Population - 1990 | 6,114 | 4,806 | 251,960,433 |
| Pop. 2000 to Now | -4.5% | -8.5% | 15.6% |
| Pop. 1990 to Now | 9.0% | 32.4% | 30.8% |
| space4 | | | |
| Population Density | 792.8 | 1,064.8 | 93.4 |
| Land Area | 8.1 | 6.3 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Vandalia, IL | Greenville, IL | United States |
| Age 0 to 4 | 4.8% | 2.1% | 5.9% |
| Age 5 to 9 | 4.5% | 3.8% | 6.1% |
| Age 10 to 14 | 4.0% | 3.9% | 6.6% |
| Age 15 to 17 | 2.9% | 3.7% | 3.9% |
| Age 18 to 20 | 3.9% | 9.6% | 4.0% |
| Age 21 to 24 | 6.0% | 8.2% | 5.2% |
| Age 25 to 34 | 15.4% | 15.2% | 13.8% |
| Age 35 to 44 | 13.4% | 15.5% | 12.9% |
| Age 45 to 54 | 13.1% | 12.0% | 12.6% |
| Age 55 to 59 | 8.6% | 4.9% | 6.7% |
| Age 60 to 64 | 7.4% | 5.3% | 6.3% |
| Age 65 to 74 | 8.4% | 6.8% | 9.6% |
| Age 75 to 84 | 6.0% | 5.0% | 4.5% |
| Age 85 and over | 1.6% | 3.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Vandalia, IL | Greenville, IL | United States |
| White | 79.7% | 73.6% | 59.4% |
| Black | 13.9% | 16.7% | 12.2% |
| Asian | 0.0% | 2.3% | 5.6% |
| Native American | 0.3% | 0.7% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.4% | 0.3% | 3.2% |
| Hispanic | 5.5% | 6.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Vandalia, IL | Greenville, IL | United States |
| Married Population | 35.3% | 31.3% | 49.8% |
| Currently Married | 34.0% | 27.7% | 48.0% |
| Married but Separated | 1.3% | 3.7% | 1.8% |
| Single Population | 64.7% | 68.7% | 50.2% |
| Never Married | 44.5% | 47.3% | 33.8% |
| Divorced | 13.3% | 15.7% | 10.8% |
| Widowed | 6.9% | 5.7% | 5.6% |
| space5 | | | |
| Household Size | 2.43 | 2.15 | 2.60 |
| Households | 2,090 | 2,185 | 124,010,992 |
| Family Households | 1,166 | 1,176 | 80,755,759 |
| Married couple, w/children | 23.8% | 29.3% | 30.5% |
| Married couple, no children | 45.0% | 34.0% | 42.9% |
| Non Family Households | 924 | 1,009 | 43,255,233 |
| Single householder, w/children | 20.6% | 33.8% | 15.8% |
| Single householder, no children | 10.6% | 2.8% | 10.8% |