| | Williamsburg, MA | South Hadley, MA | United States |
| Population | 2,623 | 18,051 | 329,725,481 |
| Female Population | 56.2% | 59.9% | 50.5% |
| Male Population | 43.8% | 40.1% | 49.5% |
| Median Age | 51.2 | 42.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 2,490 | 17,737 | 309,327,143 |
| Population - 2000 | 2,427 | 17,196 | 285,036,114 |
| Population - 1990 | 2,515 | 16,685 | 251,960,433 |
| Pop. 2000 to Now | 1.4% | 2.0% | 15.6% |
| Pop. 1990 to Now | -2.1% | 5.1% | 30.8% |
| space4 | | | |
| Population Density | 102.6 | 1,019.1 | 93.4 |
| Land Area | 25.6 | 17.7 | 3,531,905.4 |
| Water Area | 0.1 | 0.7 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Williamsburg, MA | South Hadley, MA | United States |
| Age 0 to 4 | 2.2% | 3.5% | 5.9% |
| Age 5 to 9 | 3.0% | 3.6% | 6.1% |
| Age 10 to 14 | 6.3% | 3.8% | 6.6% |
| Age 15 to 17 | 3.7% | 3.3% | 3.9% |
| Age 18 to 20 | 0.5% | 11.9% | 4.0% |
| Age 21 to 24 | 3.5% | 7.3% | 5.2% |
| Age 25 to 34 | 10.9% | 9.1% | 13.8% |
| Age 35 to 44 | 8.5% | 10.5% | 12.9% |
| Age 45 to 54 | 22.4% | 10.7% | 12.6% |
| Age 55 to 59 | 6.5% | 6.7% | 6.7% |
| Age 60 to 64 | 8.2% | 7.3% | 6.3% |
| Age 65 to 74 | 18.5% | 11.9% | 9.6% |
| Age 75 to 84 | 4.7% | 6.7% | 4.5% |
| Age 85 and over | 1.1% | 3.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Williamsburg, MA | South Hadley, MA | United States |
| White | 96.6% | 84.9% | 59.4% |
| Black | 1.1% | 1.5% | 12.2% |
| Asian | 0.0% | 5.2% | 5.6% |
| Native American | 0.7% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.0% | 2.3% | 3.2% |
| Hispanic | 1.6% | 5.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Williamsburg, MA | South Hadley, MA | United States |
| Married Population | 51.7% | 43.3% | 49.8% |
| Currently Married | 50.9% | 42.2% | 48.0% |
| Married but Separated | 0.8% | 1.2% | 1.8% |
| Single Population | 48.3% | 56.7% | 50.2% |
| Never Married | 26.6% | 38.6% | 33.8% |
| Divorced | 16.5% | 12.0% | 10.8% |
| Widowed | 5.2% | 6.1% | 5.6% |
| space5 | | | |
| Household Size | 2.24 | 2.13 | 2.60 |
| Households | 1,168 | 7,328 | 124,010,992 |
| Family Households | 734 | 4,408 | 80,755,759 |
| Married couple, w/children | 27.1% | 21.5% | 30.5% |
| Married couple, no children | 49.2% | 55.4% | 42.9% |
| Non Family Households | 434 | 2,920 | 43,255,233 |
| Single householder, w/children | 8.3% | 10.4% | 15.8% |
| Single householder, no children | 15.4% | 12.7% | 10.8% |