| | Brentwood, MO | Webster Groves, MO | United States |
| Population | 8,198 | 23,817 | 329,725,481 |
| Female Population | 50.9% | 54.8% | 50.5% |
| Male Population | 49.1% | 45.2% | 49.5% |
| Median Age | 36.6 | 39.5 | 38.4 |
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| Population - 2010 | 8,047 | 23,006 | 309,327,143 |
| Population - 2000 | 7,693 | 23,230 | 285,036,114 |
| Population - 1990 | 8,150 | 22,987 | 251,960,433 |
| Pop. 2000 to Now | 3.4% | -1.4% | 15.6% |
| Pop. 1990 to Now | -2.4% | -0.4% | 30.8% |
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| Population Density | 4,206.3 | 4,019.1 | 93.4 |
| Land Area | 1.9 | 5.9 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Brentwood, MO | Webster Groves, MO | United States |
| Age 0 to 4 | 5.6% | 6.0% | 5.9% |
| Age 5 to 9 | 3.8% | 7.1% | 6.1% |
| Age 10 to 14 | 7.4% | 6.4% | 6.6% |
| Age 15 to 17 | 1.4% | 3.6% | 3.9% |
| Age 18 to 20 | 1.9% | 4.7% | 4.0% |
| Age 21 to 24 | 4.3% | 4.4% | 5.2% |
| Age 25 to 34 | 22.0% | 10.9% | 13.8% |
| Age 35 to 44 | 17.7% | 14.4% | 12.9% |
| Age 45 to 54 | 9.5% | 10.8% | 12.6% |
| Age 55 to 59 | 7.5% | 6.7% | 6.7% |
| Age 60 to 64 | 3.6% | 7.1% | 6.3% |
| Age 65 to 74 | 9.9% | 8.9% | 9.6% |
| Age 75 to 84 | 4.4% | 4.6% | 4.5% |
| Age 85 and over | 1.1% | 4.4% | 1.9% |
| space1 | | | |
| Race | | | |
| | Brentwood, MO | Webster Groves, MO | United States |
| White | 77.8% | 85.0% | 59.4% |
| Black | 4.5% | 2.7% | 12.2% |
| Asian | 6.2% | 1.8% | 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 | 8.2% | 7.2% | 3.2% |
| Hispanic | 3.2% | 3.1% | 18.4% |
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| Marriage & Family | | | |
| | Brentwood, MO | Webster Groves, MO | United States |
| Married Population | 39.8% | 57.4% | 49.8% |
| Currently Married | 39.2% | 56.7% | 48.0% |
| Married but Separated | 0.6% | 0.7% | 1.8% |
| Single Population | 60.2% | 42.6% | 50.2% |
| Never Married | 42.4% | 26.2% | 33.8% |
| Divorced | 13.8% | 9.3% | 10.8% |
| Widowed | 4.0% | 7.1% | 5.6% |
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| Household Size | 1.96 | 2.42 | 2.60 |
| Households | 4,177 | 9,533 | 124,010,992 |
| Family Households | 1,803 | 6,109 | 80,755,759 |
| Married couple, w/children | 27.8% | 40.3% | 30.5% |
| Married couple, no children | 44.3% | 47.2% | 42.9% |
| Non Family Households | 2,374 | 3,424 | 43,255,233 |
| Single householder, w/children | 15.9% | 5.2% | 15.8% |
| Single householder, no children | 12.0% | 7.3% | 10.8% |