| | Plainfield, NH | St. Johnsbury, VT | United States |
| Population | 2,694 | 7,403 | 329,725,481 |
| Female Population | 51.1% | 49.0% | 50.5% |
| Male Population | 48.9% | 51.0% | 49.5% |
| Median Age | 41.2 | 45.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 2,365 | 7,580 | 309,327,143 |
| Population - 2000 | 2,241 | 7,571 | 285,036,114 |
| Population - 1990 | 2,056 | 7,608 | 251,960,433 |
| Pop. 2000 to Now | 7.9% | -6.6% | 15.6% |
| Pop. 1990 to Now | 17.7% | -7.1% | 30.8% |
| space4 | | | |
| Population Density | 51.6 | 203.4 | 93.4 |
| Land Area | 52.2 | 36.4 | 3,531,905.4 |
| Water Area | 0.7 | 0.4 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Plainfield, NH | St. Johnsbury, VT | United States |
| Age 0 to 4 | 7.6% | 4.1% | 5.9% |
| Age 5 to 9 | 2.5% | 4.3% | 6.1% |
| Age 10 to 14 | 6.6% | 8.7% | 6.6% |
| Age 15 to 17 | 5.1% | 4.6% | 3.9% |
| Age 18 to 20 | 5.6% | 2.6% | 4.0% |
| Age 21 to 24 | 3.1% | 3.6% | 5.2% |
| Age 25 to 34 | 14.4% | 11.4% | 13.8% |
| Age 35 to 44 | 7.7% | 10.2% | 12.9% |
| Age 45 to 54 | 12.1% | 14.9% | 12.6% |
| Age 55 to 59 | 5.2% | 6.4% | 6.7% |
| Age 60 to 64 | 10.1% | 7.2% | 6.3% |
| Age 65 to 74 | 14.2% | 13.3% | 9.6% |
| Age 75 to 84 | 4.5% | 7.0% | 4.5% |
| Age 85 and over | 1.3% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Plainfield, NH | St. Johnsbury, VT | United States |
| White | 92.9% | 92.6% | 59.4% |
| Black | 0.3% | 0.5% | 12.2% |
| Asian | 3.4% | 0.9% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 1.9% | 0.4% |
| Two or More Races | 2.9% | 1.7% | 3.2% |
| Hispanic | 0.4% | 2.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Plainfield, NH | St. Johnsbury, VT | United States |
| Married Population | 60.7% | 40.4% | 49.8% |
| Currently Married | 60.0% | 37.1% | 48.0% |
| Married but Separated | 0.7% | 3.3% | 1.8% |
| Single Population | 39.3% | 59.6% | 50.2% |
| Never Married | 29.8% | 32.8% | 33.8% |
| Divorced | 5.9% | 17.5% | 10.8% |
| Widowed | 3.6% | 9.2% | 5.6% |
| space5 | | | |
| Household Size | 2.79 | 2.22 | 2.60 |
| Households | 925 | 3,188 | 124,010,992 |
| Family Households | 762 | 1,759 | 80,755,759 |
| Married couple, w/children | 35.4% | 22.6% | 30.5% |
| Married couple, no children | 51.7% | 38.7% | 42.9% |
| Non Family Households | 163 | 1,429 | 43,255,233 |
| Single householder, w/children | 9.3% | 29.4% | 15.8% |
| Single householder, no children | 3.5% | 9.3% | 10.8% |