| | Wacissa, FL | St. Marks, FL | United States |
| Population | 458 | 298 | 329,725,481 |
| Female Population | 38.9% | 52.4% | 50.5% |
| Male Population | 61.1% | 47.7% | 49.5% |
| Median Age | 45.1 | 63.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 253 | 293 | 309,327,143 |
| Population - 2000 | 424 | 272 | 285,036,114 |
| Population - 1990 | 434 | 307 | 251,960,433 |
| Pop. 2000 to Now | -21.2% | 22.4% | 15.6% |
| Pop. 1990 to Now | -23.0% | 8.5% | 30.8% |
| space4 | | | |
| Population Density | 109.1 | 152.1 | 93.4 |
| Land Area | 4.2 | 2.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Wacissa, FL | St. Marks, FL | United States |
| Age 0 to 4 | 14.0% | 1.7% | 5.9% |
| Age 5 to 9 | 5.2% | 0.0% | 6.1% |
| Age 10 to 14 | 5.9% | 3.0% | 6.6% |
| Age 15 to 17 | 0.0% | 0.7% | 3.9% |
| Age 18 to 20 | 1.3% | 2.3% | 4.0% |
| Age 21 to 24 | 3.1% | 1.7% | 5.2% |
| Age 25 to 34 | 7.2% | 6.7% | 13.8% |
| Age 35 to 44 | 12.9% | 5.4% | 12.9% |
| Age 45 to 54 | 15.1% | 16.8% | 12.6% |
| Age 55 to 59 | 4.1% | 6.4% | 6.7% |
| Age 60 to 64 | 10.3% | 6.7% | 6.3% |
| Age 65 to 74 | 15.3% | 26.2% | 9.6% |
| Age 75 to 84 | 5.7% | 22.5% | 4.5% |
| Age 85 and over | 0.0% | 0.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Wacissa, FL | St. Marks, FL | United States |
| White | 86.0% | 96.0% | 59.4% |
| Black | 6.1% | 0.0% | 12.2% |
| Asian | 0.0% | 0.0% | 5.6% |
| Native American | 1.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.0% | 4.0% | 3.2% |
| Hispanic | 4.8% | 0.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Wacissa, FL | St. Marks, FL | United States |
| Married Population | 49.6% | 63.0% | 49.8% |
| Currently Married | 49.6% | 61.3% | 48.0% |
| Married but Separated | 0.0% | 1.8% | 1.8% |
| Single Population | 50.4% | 37.0% | 50.2% |
| Never Married | 21.3% | 6.3% | 33.8% |
| Divorced | 29.2% | 22.9% | 10.8% |
| Widowed | 0.0% | 7.7% | 5.6% |
| space5 | | | |
| Household Size | 1.95 | 1.96 | 2.60 |
| Households | 235 | 152 | 124,010,992 |
| Family Households | 127 | 117 | 80,755,759 |
| Married couple, w/children | 43.3% | 4.3% | 30.5% |
| Married couple, no children | 19.7% | 73.5% | 42.9% |
| Non Family Households | 108 | 35 | 43,255,233 |
| Single householder, w/children | 32.3% | 12.0% | 15.8% |
| Single householder, no children | 4.7% | 10.3% | 10.8% |