| | Mount Vernon, OH | Greenville, OH | United States |
| Population | 16,885 | 12,785 | 329,725,481 |
| Female Population | 53.9% | 54.2% | 50.5% |
| Male Population | 46.1% | 45.8% | 49.5% |
| Median Age | 39.3 | 45.7 | 38.4 |
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| Population - 2010 | 17,016 | 13,251 | 309,327,143 |
| Population - 2000 | 14,375 | 13,294 | 285,036,114 |
| Population - 1990 | 14,550 | 12,863 | 251,960,433 |
| Pop. 2000 to Now | 15.9% | -5.0% | 15.6% |
| Pop. 1990 to Now | 14.5% | -1.8% | 30.8% |
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| Population Density | 1,769.7 | 1,926.6 | 93.4 |
| Land Area | 9.5 | 6.6 | 3,531,905.4 |
| Water Area | 0.2 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Mount Vernon, OH | Greenville, OH | United States |
| Age 0 to 4 | 5.2% | 4.3% | 5.9% |
| Age 5 to 9 | 3.4% | 7.4% | 6.1% |
| Age 10 to 14 | 5.8% | 6.3% | 6.6% |
| Age 15 to 17 | 5.1% | 3.6% | 3.9% |
| Age 18 to 20 | 6.3% | 3.5% | 4.0% |
| Age 21 to 24 | 6.7% | 4.2% | 5.2% |
| Age 25 to 34 | 11.7% | 9.5% | 13.8% |
| Age 35 to 44 | 13.1% | 10.4% | 12.9% |
| Age 45 to 54 | 11.6% | 10.1% | 12.6% |
| Age 55 to 59 | 4.7% | 7.5% | 6.7% |
| Age 60 to 64 | 5.9% | 8.7% | 6.3% |
| Age 65 to 74 | 10.4% | 10.6% | 9.6% |
| Age 75 to 84 | 6.0% | 9.0% | 4.5% |
| Age 85 and over | 4.1% | 5.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Mount Vernon, OH | Greenville, OH | United States |
| White | 91.4% | 94.8% | 59.4% |
| Black | 0.9% | 1.3% | 12.2% |
| Asian | 0.9% | 0.0% | 5.6% |
| Native American | 0.2% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.6% | 0.1% | 0.4% |
| Two or More Races | 3.2% | 1.9% | 3.2% |
| Hispanic | 2.8% | 1.6% | 18.4% |
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| Marriage & Family | | | |
| | Mount Vernon, OH | Greenville, OH | United States |
| Married Population | 45.4% | 44.8% | 49.8% |
| Currently Married | 42.6% | 44.0% | 48.0% |
| Married but Separated | 2.8% | 0.8% | 1.8% |
| Single Population | 54.6% | 55.2% | 50.2% |
| Never Married | 33.4% | 22.5% | 33.8% |
| Divorced | 14.3% | 18.1% | 10.8% |
| Widowed | 7.0% | 14.5% | 5.6% |
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| Household Size | 2.26 | 2.10 | 2.60 |
| Households | 6,825 | 5,958 | 124,010,992 |
| Family Households | 4,142 | 3,016 | 80,755,759 |
| Married couple, w/children | 23.1% | 26.4% | 30.5% |
| Married couple, no children | 46.6% | 46.5% | 42.9% |
| Non Family Households | 2,683 | 2,942 | 43,255,233 |
| Single householder, w/children | 24.4% | 17.6% | 15.8% |
| Single householder, no children | 6.0% | 9.4% | 10.8% |