| | Westchester, IL | Lisle, IL | United States |
| Population | 16,837 | 23,982 | 329,725,481 |
| Female Population | 53.7% | 47.5% | 50.5% |
| Male Population | 46.4% | 52.5% | 49.5% |
| Median Age | 49.3 | 36.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 16,728 | 22,627 | 309,327,143 |
| Population - 2000 | 16,824 | 21,182 | 285,036,114 |
| Population - 1990 | 17,301 | 19,512 | 251,960,433 |
| Pop. 2000 to Now | -5.4% | 9.3% | 15.6% |
| Pop. 1990 to Now | -8.0% | 18.7% | 30.8% |
| space4 | | | |
| Population Density | 4,567.8 | 3,408.0 | 93.4 |
| Land Area | 3.7 | 7.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Westchester, IL | Lisle, IL | United States |
| Age 0 to 4 | 5.0% | 6.6% | 5.9% |
| Age 5 to 9 | 3.5% | 6.9% | 6.1% |
| Age 10 to 14 | 3.8% | 6.1% | 6.6% |
| Age 15 to 17 | 4.2% | 2.0% | 3.9% |
| Age 18 to 20 | 1.8% | 5.0% | 4.0% |
| Age 21 to 24 | 4.7% | 5.6% | 5.2% |
| Age 25 to 34 | 10.8% | 14.9% | 13.8% |
| Age 35 to 44 | 10.6% | 14.7% | 12.9% |
| Age 45 to 54 | 13.3% | 11.1% | 12.6% |
| Age 55 to 59 | 6.8% | 7.5% | 6.7% |
| Age 60 to 64 | 8.4% | 5.2% | 6.3% |
| Age 65 to 74 | 15.2% | 7.8% | 9.6% |
| Age 75 to 84 | 8.4% | 4.1% | 4.5% |
| Age 85 and over | 3.7% | 2.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Westchester, IL | Lisle, IL | United States |
| White | 54.0% | 69.2% | 59.4% |
| Black | 21.8% | 4.2% | 12.2% |
| Asian | 2.9% | 17.7% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.1% | 0.4% |
| Two or More Races | 0.7% | 2.9% | 3.2% |
| Hispanic | 20.7% | 5.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Westchester, IL | Lisle, IL | United States |
| Married Population | 52.3% | 54.0% | 49.8% |
| Currently Married | 51.1% | 53.2% | 48.0% |
| Married but Separated | 1.2% | 0.8% | 1.8% |
| Single Population | 47.8% | 46.0% | 50.2% |
| Never Married | 30.0% | 33.0% | 33.8% |
| Divorced | 9.5% | 8.1% | 10.8% |
| Widowed | 8.3% | 4.8% | 5.6% |
| space5 | | | |
| Household Size | 2.44 | 2.29 | 2.60 |
| Households | 6,829 | 10,077 | 124,010,992 |
| Family Households | 4,607 | 5,671 | 80,755,759 |
| Married couple, w/children | 26.3% | 37.3% | 30.5% |
| Married couple, no children | 50.2% | 47.8% | 42.9% |
| Non Family Households | 2,222 | 4,406 | 43,255,233 |
| Single householder, w/children | 8.5% | 8.8% | 15.8% |
| Single householder, no children | 15.0% | 6.0% | 10.8% |