| | Mount Vernon, MO | Marshfield, MO | United States |
| Population | 4,470 | 7,391 | 329,725,481 |
| Female Population | 53.1% | 50.0% | 50.5% |
| Male Population | 46.9% | 50.0% | 49.5% |
| Median Age | 43.6 | 32.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 4,564 | 6,681 | 309,327,143 |
| Population - 2000 | 4,017 | 5,720 | 285,036,114 |
| Population - 1990 | 3,726 | 4,374 | 251,960,433 |
| Pop. 2000 to Now | 11.5% | 34.2% | 15.6% |
| Pop. 1990 to Now | 20.2% | 75.5% | 30.8% |
| space4 | | | |
| Population Density | 1,124.5 | 1,417.3 | 93.4 |
| Land Area | 4.0 | 5.2 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Mount Vernon, MO | Marshfield, MO | United States |
| Age 0 to 4 | 4.4% | 10.7% | 5.9% |
| Age 5 to 9 | 6.9% | 7.0% | 6.1% |
| Age 10 to 14 | 5.5% | 10.6% | 6.6% |
| Age 15 to 17 | 2.6% | 2.6% | 3.9% |
| Age 18 to 20 | 2.8% | 3.3% | 4.0% |
| Age 21 to 24 | 4.0% | 4.8% | 5.2% |
| Age 25 to 34 | 11.0% | 12.9% | 13.8% |
| Age 35 to 44 | 13.2% | 14.1% | 12.9% |
| Age 45 to 54 | 14.0% | 8.5% | 12.6% |
| Age 55 to 59 | 4.0% | 4.0% | 6.7% |
| Age 60 to 64 | 7.2% | 3.5% | 6.3% |
| Age 65 to 74 | 11.6% | 9.1% | 9.6% |
| Age 75 to 84 | 6.9% | 7.2% | 4.5% |
| Age 85 and over | 5.9% | 1.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Mount Vernon, MO | Marshfield, MO | United States |
| White | 92.0% | 89.0% | 59.4% |
| Black | 0.8% | 1.2% | 12.2% |
| Asian | 0.0% | 0.0% | 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 | 2.3% | 7.9% | 3.2% |
| Hispanic | 5.0% | 1.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Mount Vernon, MO | Marshfield, MO | United States |
| Married Population | 47.3% | 55.2% | 49.8% |
| Currently Married | 43.6% | 54.0% | 48.0% |
| Married but Separated | 3.7% | 1.2% | 1.8% |
| Single Population | 52.7% | 44.8% | 50.2% |
| Never Married | 22.4% | 22.1% | 33.8% |
| Divorced | 15.7% | 16.7% | 10.8% |
| Widowed | 14.6% | 6.0% | 5.6% |
| space5 | | | |
| Household Size | 2.19 | 2.83 | 2.60 |
| Households | 1,863 | 2,558 | 124,010,992 |
| Family Households | 925 | 1,736 | 80,755,759 |
| Married couple, w/children | 29.7% | 36.0% | 30.5% |
| Married couple, no children | 44.3% | 42.7% | 42.9% |
| Non Family Households | 938 | 822 | 43,255,233 |
| Single householder, w/children | 18.6% | 17.2% | 15.8% |
| Single householder, no children | 7.4% | 4.1% | 10.8% |