| | Harpswell, ME | Costa Mesa, CA | United States |
| Population | 4,985 | 112,148 | 329,725,481 |
| Female Population | 54.8% | 49.2% | 50.5% |
| Male Population | 45.2% | 50.8% | 49.5% |
| Median Age | 60.4 | 36 | 38.4 |
| space3 | | | |
| Population - 2010 | 4,737 | 110,137 | 309,327,143 |
| Population - 2000 | 5,239 | 108,724 | 285,036,114 |
| Population - 1990 | 5,012 | 96,357 | 251,960,433 |
| Pop. 2000 to Now | -5.8% | 3.4% | 15.6% |
| Pop. 1990 to Now | -1.6% | 16.6% | 30.8% |
| space4 | | | |
| Population Density | 206.1 | 7,099.8 | 93.4 |
| Land Area | 24.2 | 15.8 | 3,531,905.4 |
| Water Area | 103.5 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Harpswell, ME | Costa Mesa, CA | United States |
| Age 0 to 4 | 2.6% | 5.7% | 5.9% |
| Age 5 to 9 | 4.5% | 4.8% | 6.1% |
| Age 10 to 14 | 3.3% | 6.1% | 6.6% |
| Age 15 to 17 | 1.5% | 3.2% | 3.9% |
| Age 18 to 20 | 3.6% | 3.3% | 4.0% |
| Age 21 to 24 | 2.5% | 5.1% | 5.2% |
| Age 25 to 34 | 5.9% | 19.6% | 13.8% |
| Age 35 to 44 | 8.6% | 15.1% | 12.9% |
| Age 45 to 54 | 9.4% | 13.4% | 12.6% |
| Age 55 to 59 | 7.6% | 6.4% | 6.7% |
| Age 60 to 64 | 16.0% | 4.9% | 6.3% |
| Age 65 to 74 | 21.5% | 7.5% | 9.6% |
| Age 75 to 84 | 10.9% | 3.0% | 4.5% |
| Age 85 and over | 2.2% | 1.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Harpswell, ME | Costa Mesa, CA | United States |
| White | 98.2% | 49.1% | 59.4% |
| Black | 0.0% | 1.3% | 12.2% |
| Asian | 0.4% | 9.0% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.6% | 0.2% |
| Other | 0.1% | 0.4% | 0.4% |
| Two or More Races | 0.6% | 3.7% | 3.2% |
| Hispanic | 0.6% | 35.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Harpswell, ME | Costa Mesa, CA | United States |
| Married Population | 64.5% | 45.1% | 49.8% |
| Currently Married | 64.1% | 43.3% | 48.0% |
| Married but Separated | 0.3% | 1.7% | 1.8% |
| Single Population | 35.5% | 54.9% | 50.2% |
| Never Married | 17.8% | 41.0% | 33.8% |
| Divorced | 12.2% | 10.6% | 10.8% |
| Widowed | 5.6% | 3.4% | 5.6% |
| space5 | | | |
| Household Size | 2.04 | 2.68 | 2.60 |
| Households | 2,431 | 41,243 | 124,010,992 |
| Family Households | 1,487 | 24,503 | 80,755,759 |
| Married couple, w/children | 14.8% | 32.7% | 30.5% |
| Married couple, no children | 74.6% | 40.8% | 42.9% |
| Non Family Households | 944 | 16,740 | 43,255,233 |
| Single householder, w/children | 7.1% | 14.8% | 15.8% |
| Single householder, no children | 3.6% | 11.8% | 10.8% |