| | Adamstown, MD | Mount Rainier, MD | United States |
| Population | 2,212 | 8,290 | 329,725,481 |
| Female Population | 47.5% | 50.3% | 50.5% |
| Male Population | 52.5% | 49.8% | 49.5% |
| Median Age | 42.6 | 40.8 | 38.4 |
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| Population - 2010 | 2,134 | 7,835 | 309,327,143 |
| Population - 2000 | 862 | 8,498 | 285,036,114 |
| Population - 1990 | 646 | 7,954 | 251,960,433 |
| Pop. 2000 to Now | 219.0% | -4.5% | 15.6% |
| Pop. 1990 to Now | 325.7% | 2.1% | 30.8% |
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| Population Density | 672.5 | 13,034.6 | 93.4 |
| Land Area | 3.3 | 0.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Adamstown, MD | Mount Rainier, MD | United States |
| Age 0 to 4 | 3.8% | 5.2% | 5.9% |
| Age 5 to 9 | 7.1% | 5.3% | 6.1% |
| Age 10 to 14 | 7.4% | 3.2% | 6.6% |
| Age 15 to 17 | 3.6% | 4.1% | 3.9% |
| Age 18 to 20 | 2.8% | 3.8% | 4.0% |
| Age 21 to 24 | 9.1% | 4.7% | 5.2% |
| Age 25 to 34 | 5.3% | 13.8% | 13.8% |
| Age 35 to 44 | 15.2% | 18.6% | 12.9% |
| Age 45 to 54 | 19.7% | 15.0% | 12.6% |
| Age 55 to 59 | 11.8% | 5.3% | 6.7% |
| Age 60 to 64 | 3.9% | 9.0% | 6.3% |
| Age 65 to 74 | 8.7% | 10.0% | 9.6% |
| Age 75 to 84 | 1.2% | 1.1% | 4.5% |
| Age 85 and over | 0.4% | 1.0% | 1.9% |
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| Race | | | |
| | Adamstown, MD | Mount Rainier, MD | United States |
| White | 82.4% | 18.7% | 59.4% |
| Black | 8.1% | 47.4% | 12.2% |
| Asian | 3.0% | 1.2% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.5% | 0.4% |
| Two or More Races | 1.2% | 1.3% | 3.2% |
| Hispanic | 5.3% | 30.9% | 18.4% |
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| Marriage & Family | | | |
| | Adamstown, MD | Mount Rainier, MD | United States |
| Married Population | 66.0% | 44.3% | 49.8% |
| Currently Married | 64.3% | 42.6% | 48.0% |
| Married but Separated | 1.8% | 1.7% | 1.8% |
| Single Population | 34.0% | 55.7% | 50.2% |
| Never Married | 27.5% | 42.8% | 33.8% |
| Divorced | 5.3% | 8.1% | 10.8% |
| Widowed | 1.2% | 4.9% | 5.6% |
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| Household Size | 3.08 | 1.99 | 2.60 |
| Households | 718 | 4,163 | 124,010,992 |
| Family Households | 612 | 1,888 | 80,755,759 |
| Married couple, w/children | 35.8% | 29.9% | 30.5% |
| Married couple, no children | 55.6% | 45.4% | 42.9% |
| Non Family Households | 106 | 2,275 | 43,255,233 |
| Single householder, w/children | 3.3% | 15.1% | 15.8% |
| Single householder, no children | 5.4% | 9.6% | 10.8% |