| | The Plains, OH | Mount Vernon, OH | United States |
| Population | 2,644 | 16,885 | 329,725,481 |
| Female Population | 55.8% | 53.9% | 50.5% |
| Male Population | 44.2% | 46.1% | 49.5% |
| Median Age | 54.3 | 39.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,115 | 17,016 | 309,327,143 |
| Population - 2000 | 2,931 | 14,375 | 285,036,114 |
| Population - 1990 | 2,644 | 14,550 | 251,960,433 |
| Pop. 2000 to Now | 1.1% | 15.9% | 15.6% |
| Pop. 1990 to Now | 12.0% | 14.5% | 30.8% |
| space4 | | | |
| Population Density | 1,159.7 | 1,769.7 | 93.4 |
| Land Area | 2.3 | 9.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | The Plains, OH | Mount Vernon, OH | United States |
| Age 0 to 4 | 3.2% | 5.2% | 5.9% |
| Age 5 to 9 | 3.4% | 3.4% | 6.1% |
| Age 10 to 14 | 3.7% | 5.8% | 6.6% |
| Age 15 to 17 | 0.6% | 5.1% | 3.9% |
| Age 18 to 20 | 1.4% | 6.3% | 4.0% |
| Age 21 to 24 | 2.7% | 6.7% | 5.2% |
| Age 25 to 34 | 9.8% | 11.7% | 13.8% |
| Age 35 to 44 | 13.3% | 13.1% | 12.9% |
| Age 45 to 54 | 14.0% | 11.6% | 12.6% |
| Age 55 to 59 | 8.3% | 4.7% | 6.7% |
| Age 60 to 64 | 8.7% | 5.9% | 6.3% |
| Age 65 to 74 | 20.5% | 10.4% | 9.6% |
| Age 75 to 84 | 6.0% | 6.0% | 4.5% |
| Age 85 and over | 4.4% | 4.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | The Plains, OH | Mount Vernon, OH | United States |
| White | 93.3% | 91.4% | 59.4% |
| Black | 0.7% | 0.9% | 12.2% |
| Asian | 0.0% | 0.9% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.6% | 0.4% |
| Two or More Races | 6.0% | 3.2% | 3.2% |
| Hispanic | 0.0% | 2.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | The Plains, OH | Mount Vernon, OH | United States |
| Married Population | 35.9% | 45.4% | 49.8% |
| Currently Married | 35.8% | 42.6% | 48.0% |
| Married but Separated | 0.1% | 2.8% | 1.8% |
| Single Population | 64.1% | 54.6% | 50.2% |
| Never Married | 33.0% | 33.4% | 33.8% |
| Divorced | 11.1% | 14.3% | 10.8% |
| Widowed | 20.0% | 7.0% | 5.6% |
| space5 | | | |
| Household Size | 1.70 | 2.26 | 2.60 |
| Households | 1,479 | 6,825 | 124,010,992 |
| Family Households | 623 | 4,142 | 80,755,759 |
| Married couple, w/children | 21.7% | 23.1% | 30.5% |
| Married couple, no children | 47.5% | 46.6% | 42.9% |
| Non Family Households | 856 | 2,683 | 43,255,233 |
| Single householder, w/children | 7.7% | 24.4% | 15.8% |
| Single householder, no children | 23.1% | 6.0% | 10.8% |