| | Westport, CT | Mountain Brook, AL | United States |
| Population | 27,168 | 22,184 | 329,725,481 |
| Female Population | 49.9% | 51.6% | 50.5% |
| Male Population | 50.1% | 48.4% | 49.5% |
| Median Age | 46.1 | 41.9 | 38.4 |
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| Population - 2010 | 26,452 | 20,316 | 309,327,143 |
| Population - 2000 | 25,749 | 20,604 | 285,036,114 |
| Population - 1990 | 24,410 | 19,810 | 251,960,433 |
| Pop. 2000 to Now | 10.5% | -2.8% | 15.6% |
| Pop. 1990 to Now | 16.5% | 1.1% | 30.8% |
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| Population Density | 1,361.1 | 1,729.8 | 93.4 |
| Land Area | 20.0 | 12.8 | 3,531,905.4 |
| Water Area | 13.5 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Westport, CT | Mountain Brook, AL | United States |
| Age 0 to 4 | 4.9% | 8.3% | 5.9% |
| Age 5 to 9 | 7.2% | 6.8% | 6.1% |
| Age 10 to 14 | 9.6% | 7.5% | 6.6% |
| Age 15 to 17 | 5.7% | 5.1% | 3.9% |
| Age 18 to 20 | 2.9% | 3.0% | 4.0% |
| Age 21 to 24 | 3.6% | 1.6% | 5.2% |
| Age 25 to 34 | 4.0% | 10.3% | 13.8% |
| Age 35 to 44 | 10.0% | 10.9% | 12.9% |
| Age 45 to 54 | 17.3% | 16.0% | 12.6% |
| Age 55 to 59 | 10.3% | 5.0% | 6.7% |
| Age 60 to 64 | 7.5% | 7.0% | 6.3% |
| Age 65 to 74 | 10.1% | 12.1% | 9.6% |
| Age 75 to 84 | 5.0% | 3.1% | 4.5% |
| Age 85 and over | 1.8% | 3.2% | 1.9% |
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| Race | | | |
| | Westport, CT | Mountain Brook, AL | United States |
| White | 83.6% | 97.7% | 59.4% |
| Black | 0.9% | 0.4% | 12.2% |
| Asian | 5.7% | 1.0% | 5.6% |
| Native American | 0.2% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.6% | 0.2% | 0.4% |
| Two or More Races | 2.4% | 0.5% | 3.2% |
| Hispanic | 6.5% | 0.2% | 18.4% |
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| Marriage & Family | | | |
| | Westport, CT | Mountain Brook, AL | United States |
| Married Population | 65.0% | 70.0% | 49.8% |
| Currently Married | 64.3% | 69.9% | 48.0% |
| Married but Separated | 0.8% | 0.1% | 1.8% |
| Single Population | 35.0% | 30.0% | 50.2% |
| Never Married | 23.6% | 21.5% | 33.8% |
| Divorced | 6.6% | 4.5% | 10.8% |
| Widowed | 4.8% | 4.0% | 5.6% |
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| Household Size | 2.85 | 2.65 | 2.60 |
| Households | 9,478 | 8,365 | 124,010,992 |
| Family Households | 7,338 | 6,315 | 80,755,759 |
| Married couple, w/children | 44.6% | 48.8% | 30.5% |
| Married couple, no children | 46.3% | 44.6% | 42.9% |
| Non Family Households | 2,140 | 2,050 | 43,255,233 |
| Single householder, w/children | 4.5% | 3.4% | 15.8% |
| Single householder, no children | 4.6% | 3.2% | 10.8% |