| | Essex, MD | Spencer, WV | United States |
| Population | 40,710 | 2,186 | 329,725,481 |
| Female Population | 53.3% | 51.7% | 50.5% |
| Male Population | 46.7% | 48.4% | 49.5% |
| Median Age | 38.9 | 42.7 | 38.4 |
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| Population - 2010 | 38,790 | 2,279 | 309,327,143 |
| Population - 2000 | 39,078 | 2,352 | 285,036,114 |
| Population - 1990 | 40,872 | 2,279 | 251,960,433 |
| Pop. 2000 to Now | 0.9% | -15.4% | 15.6% |
| Pop. 1990 to Now | -3.6% | -12.7% | 30.8% |
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| Population Density | 4,397.3 | 1,737.7 | 93.4 |
| Land Area | 9.3 | 1.3 | 3,531,905.4 |
| Water Area | 2.6 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Essex, MD | Spencer, WV | United States |
| Age 0 to 4 | 6.1% | 5.1% | 5.9% |
| Age 5 to 9 | 6.7% | 11.3% | 6.1% |
| Age 10 to 14 | 6.4% | 5.3% | 6.6% |
| Age 15 to 17 | 3.7% | 2.4% | 3.9% |
| Age 18 to 20 | 2.7% | 3.2% | 4.0% |
| Age 21 to 24 | 3.9% | 2.7% | 5.2% |
| Age 25 to 34 | 15.8% | 11.0% | 13.8% |
| Age 35 to 44 | 10.9% | 13.0% | 12.9% |
| Age 45 to 54 | 13.8% | 11.0% | 12.6% |
| Age 55 to 59 | 7.2% | 6.8% | 6.7% |
| Age 60 to 64 | 7.1% | 8.4% | 6.3% |
| Age 65 to 74 | 9.4% | 8.8% | 9.6% |
| Age 75 to 84 | 4.5% | 7.3% | 4.5% |
| Age 85 and over | 1.9% | 3.7% | 1.9% |
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| Race | | | |
| | Essex, MD | Spencer, WV | United States |
| White | 57.8% | 95.1% | 59.4% |
| Black | 29.4% | 0.1% | 12.2% |
| Asian | 1.7% | 1.7% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.0% | 0.4% |
| Two or More Races | 4.4% | 2.6% | 3.2% |
| Hispanic | 6.2% | 0.4% | 18.4% |
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| Marriage & Family | | | |
| | Essex, MD | Spencer, WV | United States |
| Married Population | 42.2% | 30.5% | 49.8% |
| Currently Married | 39.4% | 28.8% | 48.0% |
| Married but Separated | 2.8% | 1.7% | 1.8% |
| Single Population | 57.8% | 69.5% | 50.2% |
| Never Married | 35.9% | 27.1% | 33.8% |
| Divorced | 14.2% | 24.8% | 10.8% |
| Widowed | 7.8% | 17.6% | 5.6% |
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| Household Size | 2.58 | 2.26 | 2.60 |
| Households | 15,702 | 940 | 124,010,992 |
| Family Households | 9,472 | 406 | 80,755,759 |
| Married couple, w/children | 21.8% | 28.8% | 30.5% |
| Married couple, no children | 37.5% | 28.3% | 42.9% |
| Non Family Households | 6,230 | 534 | 43,255,233 |
| Single householder, w/children | 25.9% | 19.2% | 15.8% |
| Single householder, no children | 14.8% | 23.6% | 10.8% |