| | Petersburg, IL | Lombard, IL | United States |
| Population | 2,515 | 44,311 | 329,725,481 |
| Female Population | 48.9% | 51.6% | 50.5% |
| Male Population | 51.1% | 48.5% | 49.5% |
| Median Age | 39.9 | 37.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 2,342 | 43,514 | 309,327,143 |
| Population - 2000 | 2,299 | 42,322 | 285,036,114 |
| Population - 1990 | 2,261 | 39,408 | 251,960,433 |
| Pop. 2000 to Now | -4.0% | 3.9% | 15.6% |
| Pop. 1990 to Now | -2.4% | 11.6% | 30.8% |
| space4 | | | |
| Population Density | 1,610.1 | 4,340.8 | 93.4 |
| Land Area | 1.6 | 10.2 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Petersburg, IL | Lombard, IL | United States |
| Age 0 to 4 | 5.8% | 6.0% | 5.9% |
| Age 5 to 9 | 5.0% | 6.1% | 6.1% |
| Age 10 to 14 | 5.8% | 5.6% | 6.6% |
| Age 15 to 17 | 4.5% | 3.0% | 3.9% |
| Age 18 to 20 | 2.0% | 3.7% | 4.0% |
| Age 21 to 24 | 8.7% | 4.7% | 5.2% |
| Age 25 to 34 | 11.2% | 16.6% | 13.8% |
| Age 35 to 44 | 15.6% | 13.3% | 12.9% |
| Age 45 to 54 | 12.8% | 11.6% | 12.6% |
| Age 55 to 59 | 8.6% | 7.3% | 6.7% |
| Age 60 to 64 | 2.7% | 6.3% | 6.3% |
| Age 65 to 74 | 7.2% | 8.6% | 9.6% |
| Age 75 to 84 | 5.8% | 4.6% | 4.5% |
| Age 85 and over | 4.2% | 2.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Petersburg, IL | Lombard, IL | United States |
| White | 93.5% | 70.2% | 59.4% |
| Black | 0.5% | 4.6% | 12.2% |
| Asian | 0.3% | 12.1% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 4.1% | 3.1% | 3.2% |
| Hispanic | 1.6% | 9.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Petersburg, IL | Lombard, IL | United States |
| Married Population | 47.2% | 54.4% | 49.8% |
| Currently Married | 46.9% | 53.8% | 48.0% |
| Married but Separated | 0.2% | 0.6% | 1.8% |
| Single Population | 52.8% | 45.6% | 50.2% |
| Never Married | 28.1% | 31.2% | 33.8% |
| Divorced | 18.5% | 8.5% | 10.8% |
| Widowed | 6.2% | 6.0% | 5.6% |
| space5 | | | |
| Household Size | 2.27 | 2.54 | 2.60 |
| Households | 1,097 | 17,211 | 124,010,992 |
| Family Households | 689 | 11,280 | 80,755,759 |
| Married couple, w/children | 30.2% | 34.7% | 30.5% |
| Married couple, no children | 32.7% | 44.6% | 42.9% |
| Non Family Households | 408 | 5,931 | 43,255,233 |
| Single householder, w/children | 19.7% | 9.6% | 15.8% |
| Single householder, no children | 17.4% | 11.1% | 10.8% |