| | Mount Joy township (Adams County), PA | Mount Joy township, PA | United States |
| Population | 3,764 | 10,672 | 329,725,481 |
| Female Population | 47.7% | 47.5% | 50.5% |
| Male Population | 52.3% | 52.5% | 49.5% |
| Median Age | 47.6 | 37.2 | 38.4 |
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| Population - 2010 | 3,689 | 9,924 | 309,327,143 |
| Population - 2000 | 3,232 | 7,944 | 285,036,114 |
| Population - 1990 | 2,848 | 6,227 | 251,960,433 |
| Pop. 2000 to Now | 15.4% | 41.9% | 15.6% |
| Pop. 1990 to Now | 30.9% | 81.1% | 30.8% |
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| Population Density | 144.8 | 383.4 | 93.4 |
| Land Area | 26.0 | 27.8 | 3,531,905.4 |
| Water Area | 0.2 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Mount Joy township (Adams County), PA | Mount Joy township, PA | United States |
| Age 0 to 4 | 3.7% | 8.2% | 5.9% |
| Age 5 to 9 | 6.2% | 7.6% | 6.1% |
| Age 10 to 14 | 9.5% | 4.0% | 6.6% |
| Age 15 to 17 | 3.1% | 4.0% | 3.9% |
| Age 18 to 20 | 1.7% | 2.7% | 4.0% |
| Age 21 to 24 | 4.7% | 2.8% | 5.2% |
| Age 25 to 34 | 9.3% | 15.4% | 13.8% |
| Age 35 to 44 | 7.7% | 13.0% | 12.9% |
| Age 45 to 54 | 20.5% | 16.2% | 12.6% |
| Age 55 to 59 | 4.9% | 8.4% | 6.7% |
| Age 60 to 64 | 5.3% | 4.3% | 6.3% |
| Age 65 to 74 | 14.4% | 7.2% | 9.6% |
| Age 75 to 84 | 8.0% | 4.8% | 4.5% |
| Age 85 and over | 1.1% | 1.4% | 1.9% |
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| Race | | | |
| | Mount Joy township (Adams County), PA | Mount Joy township, PA | United States |
| White | 89.9% | 87.1% | 59.4% |
| Black | 1.0% | 0.7% | 12.2% |
| Asian | 0.0% | 1.8% | 5.6% |
| Native American | 0.0% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.2% | 2.4% | 3.2% |
| Hispanic | 6.9% | 7.7% | 18.4% |
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| Marriage & Family | | | |
| | Mount Joy township (Adams County), PA | Mount Joy township, PA | United States |
| Married Population | 58.9% | 69.2% | 49.8% |
| Currently Married | 58.4% | 68.6% | 48.0% |
| Married but Separated | 0.5% | 0.6% | 1.8% |
| Single Population | 41.1% | 30.8% | 50.2% |
| Never Married | 25.6% | 21.3% | 33.8% |
| Divorced | 9.3% | 6.9% | 10.8% |
| Widowed | 6.2% | 2.6% | 5.6% |
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| Household Size | 2.53 | 2.65 | 2.60 |
| Households | 1,450 | 4,024 | 124,010,992 |
| Family Households | 994 | 3,173 | 80,755,759 |
| Married couple, w/children | 37.1% | 33.4% | 30.5% |
| Married couple, no children | 47.2% | 55.8% | 42.9% |
| Non Family Households | 456 | 851 | 43,255,233 |
| Single householder, w/children | 7.5% | 8.2% | 15.8% |
| Single householder, no children | 8.1% | 2.6% | 10.8% |