| | Rockport, ME | Port St. Lucie, FL | United States |
| Population | 3,615 | 202,177 | 329,725,481 |
| Female Population | 53.6% | 50.8% | 50.5% |
| Male Population | 46.4% | 49.3% | 49.5% |
| Median Age | 46.1 | 42.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,329 | 164,860 | 309,327,143 |
| Population - 2000 | 3,209 | 88,769 | 285,036,114 |
| Population - 1990 | 2,854 | 57,058 | 251,960,433 |
| Pop. 2000 to Now | 5.6% | 136.3% | 15.6% |
| Pop. 1990 to Now | 18.8% | 267.6% | 30.8% |
| space4 | | | |
| Population Density | 167.1 | 1,696.3 | 93.4 |
| Land Area | 21.6 | 119.2 | 3,531,905.4 |
| Water Area | 11.7 | 1.6 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Rockport, ME | Port St. Lucie, FL | United States |
| Age 0 to 4 | 3.4% | 5.3% | 5.9% |
| Age 5 to 9 | 5.1% | 5.8% | 6.1% |
| Age 10 to 14 | 7.7% | 6.7% | 6.6% |
| Age 15 to 17 | 3.5% | 3.9% | 3.9% |
| Age 18 to 20 | 3.0% | 2.8% | 4.0% |
| Age 21 to 24 | 5.2% | 4.1% | 5.2% |
| Age 25 to 34 | 10.6% | 12.2% | 13.8% |
| Age 35 to 44 | 8.7% | 12.4% | 12.9% |
| Age 45 to 54 | 17.3% | 13.1% | 12.6% |
| Age 55 to 59 | 7.9% | 6.7% | 6.7% |
| Age 60 to 64 | 6.5% | 6.8% | 6.3% |
| Age 65 to 74 | 12.6% | 11.5% | 9.6% |
| Age 75 to 84 | 5.6% | 7.1% | 4.5% |
| Age 85 and over | 2.8% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Rockport, ME | Port St. Lucie, FL | United States |
| White | 96.2% | 54.6% | 59.4% |
| Black | 0.2% | 17.3% | 12.2% |
| Asian | 1.2% | 2.0% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.5% | 0.4% |
| Two or More Races | 1.6% | 3.6% | 3.2% |
| Hispanic | 0.8% | 21.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Rockport, ME | Port St. Lucie, FL | United States |
| Married Population | 52.8% | 53.1% | 49.8% |
| Currently Married | 51.9% | 51.8% | 48.0% |
| Married but Separated | 0.8% | 1.3% | 1.8% |
| Single Population | 47.2% | 46.9% | 50.2% |
| Never Married | 25.0% | 27.9% | 33.8% |
| Divorced | 17.3% | 12.9% | 10.8% |
| Widowed | 5.0% | 6.1% | 5.6% |
| space5 | | | |
| Household Size | 2.60 | 2.81 | 2.60 |
| Households | 1,364 | 71,609 | 124,010,992 |
| Family Households | 1,037 | 53,535 | 80,755,759 |
| Married couple, w/children | 22.5% | 28.4% | 30.5% |
| Married couple, no children | 53.0% | 45.5% | 42.9% |
| Non Family Households | 327 | 18,074 | 43,255,233 |
| Single householder, w/children | 12.0% | 14.8% | 15.8% |
| Single householder, no children | 12.5% | 11.3% | 10.8% |