| | Ellisville, MO | Westmont, IL | United States |
| Population | 9,908 | 24,632 | 329,725,481 |
| Female Population | 54.7% | 52.7% | 50.5% |
| Male Population | 45.3% | 47.3% | 49.5% |
| Median Age | 45.1 | 40.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 9,299 | 24,694 | 309,327,143 |
| Population - 2000 | 9,104 | 24,554 | 285,036,114 |
| Population - 1990 | 7,545 | 21,228 | 251,960,433 |
| Pop. 2000 to Now | 8.2% | -1.2% | 15.6% |
| Pop. 1990 to Now | 30.5% | 14.3% | 30.8% |
| space4 | | | |
| Population Density | 2,255.9 | 4,927.4 | 93.4 |
| Land Area | 4.4 | 5.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Ellisville, MO | Westmont, IL | United States |
| Age 0 to 4 | 5.8% | 6.4% | 5.9% |
| Age 5 to 9 | 5.1% | 5.6% | 6.1% |
| Age 10 to 14 | 6.3% | 4.9% | 6.6% |
| Age 15 to 17 | 4.5% | 3.3% | 3.9% |
| Age 18 to 20 | 2.0% | 2.7% | 4.0% |
| Age 21 to 24 | 3.2% | 4.5% | 5.2% |
| Age 25 to 34 | 11.8% | 15.1% | 13.8% |
| Age 35 to 44 | 10.9% | 12.7% | 12.9% |
| Age 45 to 54 | 11.6% | 11.3% | 12.6% |
| Age 55 to 59 | 6.5% | 7.0% | 6.7% |
| Age 60 to 64 | 8.0% | 7.8% | 6.3% |
| Age 65 to 74 | 13.3% | 10.9% | 9.6% |
| Age 75 to 84 | 6.4% | 5.5% | 4.5% |
| Age 85 and over | 4.6% | 2.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Ellisville, MO | Westmont, IL | United States |
| White | 81.1% | 63.9% | 59.4% |
| Black | 1.6% | 6.2% | 12.2% |
| Asian | 4.4% | 12.9% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.3% | 0.4% |
| Two or More Races | 6.8% | 3.5% | 3.2% |
| Hispanic | 6.0% | 13.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Ellisville, MO | Westmont, IL | United States |
| Married Population | 58.4% | 51.9% | 49.8% |
| Currently Married | 56.8% | 50.8% | 48.0% |
| Married but Separated | 1.5% | 1.1% | 1.8% |
| Single Population | 41.6% | 48.1% | 50.2% |
| Never Married | 21.8% | 31.8% | 33.8% |
| Divorced | 9.9% | 9.2% | 10.8% |
| Widowed | 9.9% | 7.0% | 5.6% |
| space5 | | | |
| Household Size | 2.43 | 2.33 | 2.60 |
| Households | 4,010 | 10,401 | 124,010,992 |
| Family Households | 2,788 | 6,285 | 80,755,759 |
| Married couple, w/children | 33.8% | 29.0% | 30.5% |
| Married couple, no children | 45.9% | 48.3% | 42.9% |
| Non Family Households | 1,222 | 4,116 | 43,255,233 |
| Single householder, w/children | 9.9% | 14.2% | 15.8% |
| Single householder, no children | 10.4% | 8.4% | 10.8% |