| | Preston, CT | Union, ME | United States |
| Population | 4,778 | 2,738 | 329,725,481 |
| Female Population | 53.6% | 55.0% | 50.5% |
| Male Population | 46.4% | 45.0% | 49.5% |
| Median Age | 45.6 | 41.2 | 38.4 |
| space3 | | | |
| Population - 2010 | 4,724 | 2,259 | 309,327,143 |
| Population - 2000 | 4,688 | 2,209 | 285,036,114 |
| Population - 1990 | 5,006 | 1,989 | 251,960,433 |
| Pop. 2000 to Now | -1.3% | 3.0% | 15.6% |
| Pop. 1990 to Now | -7.5% | 14.4% | 30.8% |
| space4 | | | |
| Population Density | 155.0 | 85.2 | 93.4 |
| Land Area | 30.8 | 32.2 | 3,531,905.4 |
| Water Area | 0.9 | 2.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Preston, CT | Union, ME | United States |
| Age 0 to 4 | 5.2% | 10.7% | 5.9% |
| Age 5 to 9 | 5.3% | 4.6% | 6.1% |
| Age 10 to 14 | 6.2% | 4.4% | 6.6% |
| Age 15 to 17 | 3.0% | 4.4% | 3.9% |
| Age 18 to 20 | 3.4% | 3.0% | 4.0% |
| Age 21 to 24 | 6.2% | 4.1% | 5.2% |
| Age 25 to 34 | 12.0% | 12.3% | 13.8% |
| Age 35 to 44 | 8.4% | 9.7% | 12.9% |
| Age 45 to 54 | 13.7% | 12.3% | 12.6% |
| Age 55 to 59 | 8.6% | 6.8% | 6.7% |
| Age 60 to 64 | 9.0% | 6.0% | 6.3% |
| Age 65 to 74 | 13.9% | 15.0% | 9.6% |
| Age 75 to 84 | 4.2% | 4.8% | 4.5% |
| Age 85 and over | 1.0% | 2.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Preston, CT | Union, ME | United States |
| White | 91.9% | 94.8% | 59.4% |
| Black | 0.9% | 0.2% | 12.2% |
| Asian | 2.0% | 0.2% | 5.6% |
| Native American | 0.1% | 0.5% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.9% | 0.0% | 0.4% |
| Two or More Races | 2.5% | 3.9% | 3.2% |
| Hispanic | 1.7% | 0.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Preston, CT | Union, ME | United States |
| Married Population | 58.4% | 55.8% | 49.8% |
| Currently Married | 57.9% | 54.4% | 48.0% |
| Married but Separated | 0.5% | 1.4% | 1.8% |
| Single Population | 41.6% | 44.2% | 50.2% |
| Never Married | 25.6% | 21.1% | 33.8% |
| Divorced | 11.7% | 16.8% | 10.8% |
| Widowed | 4.4% | 6.3% | 5.6% |
| space5 | | | |
| Household Size | 2.60 | 2.59 | 2.60 |
| Households | 1,835 | 1,041 | 124,010,992 |
| Family Households | 1,327 | 672 | 80,755,759 |
| Married couple, w/children | 29.8% | 40.6% | 30.5% |
| Married couple, no children | 51.8% | 45.1% | 42.9% |
| Non Family Households | 508 | 369 | 43,255,233 |
| Single householder, w/children | 6.5% | 10.1% | 15.8% |
| Single householder, no children | 11.8% | 4.2% | 10.8% |