| | Memphis, MO | Seneca, SC | United States |
| Population | 1,773 | 8,734 | 329,725,481 |
| Female Population | 58.4% | 53.0% | 50.5% |
| Male Population | 41.6% | 47.0% | 49.5% |
| Median Age | 41.1 | 39.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,812 | 8,111 | 309,327,143 |
| Population - 2000 | 2,061 | 7,652 | 285,036,114 |
| Population - 1990 | 2,094 | 7,726 | 251,960,433 |
| Pop. 2000 to Now | -11.9% | 11.9% | 15.6% |
| Pop. 1990 to Now | -13.3% | 10.9% | 30.8% |
| space4 | | | |
| Population Density | 1,138.0 | 1,110.5 | 93.4 |
| Land Area | 1.6 | 7.9 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Memphis, MO | Seneca, SC | United States |
| Age 0 to 4 | 4.5% | 8.3% | 5.9% |
| Age 5 to 9 | 6.1% | 3.7% | 6.1% |
| Age 10 to 14 | 6.3% | 4.5% | 6.6% |
| Age 15 to 17 | 5.8% | 2.5% | 3.9% |
| Age 18 to 20 | 5.6% | 3.9% | 4.0% |
| Age 21 to 24 | 3.8% | 1.8% | 5.2% |
| Age 25 to 34 | 8.4% | 19.6% | 13.8% |
| Age 35 to 44 | 15.2% | 11.4% | 12.9% |
| Age 45 to 54 | 8.9% | 9.3% | 12.6% |
| Age 55 to 59 | 5.4% | 6.6% | 6.7% |
| Age 60 to 64 | 9.5% | 8.4% | 6.3% |
| Age 65 to 74 | 10.3% | 10.6% | 9.6% |
| Age 75 to 84 | 4.6% | 7.1% | 4.5% |
| Age 85 and over | 5.5% | 2.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Memphis, MO | Seneca, SC | United States |
| White | 97.0% | 69.3% | 59.4% |
| Black | 0.1% | 20.7% | 12.2% |
| Asian | 0.0% | 0.2% | 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 | 2.9% | 1.6% | 3.2% |
| Hispanic | 0.0% | 7.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Memphis, MO | Seneca, SC | United States |
| Married Population | 42.7% | 45.0% | 49.8% |
| Currently Married | 42.3% | 41.8% | 48.0% |
| Married but Separated | 0.4% | 3.2% | 1.8% |
| Single Population | 57.3% | 55.0% | 50.2% |
| Never Married | 30.0% | 34.2% | 33.8% |
| Divorced | 16.9% | 13.2% | 10.8% |
| Widowed | 10.4% | 7.6% | 5.6% |
| space5 | | | |
| Household Size | 2.32 | 2.36 | 2.60 |
| Households | 731 | 3,678 | 124,010,992 |
| Family Households | 382 | 2,025 | 80,755,759 |
| Married couple, w/children | 28.5% | 21.3% | 30.5% |
| Married couple, no children | 49.2% | 51.6% | 42.9% |
| Non Family Households | 349 | 1,653 | 43,255,233 |
| Single householder, w/children | 16.5% | 16.4% | 15.8% |
| Single householder, no children | 5.8% | 10.7% | 10.8% |