| | Crestwood, MO | Affton, MO | United States |
| Population | 12,347 | 18,925 | 329,725,481 |
| Female Population | 50.4% | 49.0% | 50.5% |
| Male Population | 49.6% | 51.0% | 49.5% |
| Median Age | 40.6 | 42.5 | 38.4 |
| space3 | | | |
| Population - 2010 | 11,884 | 20,115 | 309,327,143 |
| Population - 2000 | 11,863 | 20,535 | 285,036,114 |
| Population - 1990 | 11,234 | 21,106 | 251,960,433 |
| Pop. 2000 to Now | -0.3% | 4.9% | 15.6% |
| Pop. 1990 to Now | 5.3% | 2.1% | 30.8% |
| space4 | | | |
| Population Density | 3,440.2 | 4,150.2 | 93.4 |
| Land Area | 3.6 | 4.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Crestwood, MO | Affton, MO | United States |
| Age 0 to 4 | 5.2% | 4.9% | 5.9% |
| Age 5 to 9 | 6.3% | 6.0% | 6.1% |
| Age 10 to 14 | 6.1% | 3.7% | 6.6% |
| Age 15 to 17 | 3.8% | 2.5% | 3.9% |
| Age 18 to 20 | 1.6% | 2.4% | 4.0% |
| Age 21 to 24 | 1.9% | 6.0% | 5.2% |
| Age 25 to 34 | 14.5% | 14.5% | 13.8% |
| Age 35 to 44 | 16.0% | 14.5% | 12.9% |
| Age 45 to 54 | 10.6% | 12.1% | 12.6% |
| Age 55 to 59 | 9.9% | 7.3% | 6.7% |
| Age 60 to 64 | 6.1% | 7.6% | 6.3% |
| Age 65 to 74 | 9.1% | 10.5% | 9.6% |
| Age 75 to 84 | 6.0% | 4.7% | 4.5% |
| Age 85 and over | 2.9% | 3.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Crestwood, MO | Affton, MO | United States |
| White | 91.0% | 87.4% | 59.4% |
| Black | 1.8% | 2.8% | 12.2% |
| Asian | 1.4% | 2.3% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.0% | 0.4% |
| Two or More Races | 2.1% | 4.0% | 3.2% |
| Hispanic | 3.5% | 3.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Crestwood, MO | Affton, MO | United States |
| Married Population | 63.7% | 51.4% | 49.8% |
| Currently Married | 61.8% | 50.7% | 48.0% |
| Married but Separated | 1.9% | 0.7% | 1.8% |
| Single Population | 36.3% | 48.6% | 50.2% |
| Never Married | 20.7% | 29.3% | 33.8% |
| Divorced | 11.1% | 13.7% | 10.8% |
| Widowed | 4.5% | 5.6% | 5.6% |
| space5 | | | |
| Household Size | 2.55 | 2.20 | 2.60 |
| Households | 4,842 | 8,612 | 124,010,992 |
| Family Households | 3,607 | 4,837 | 80,755,759 |
| Married couple, w/children | 36.6% | 28.4% | 30.5% |
| Married couple, no children | 46.4% | 50.3% | 42.9% |
| Non Family Households | 1,235 | 3,775 | 43,255,233 |
| Single householder, w/children | 6.2% | 10.8% | 15.8% |
| Single householder, no children | 10.9% | 10.5% | 10.8% |