| Williamstown - Population Change | FIPS Code=17085 |
| Absolute Population Change, 1970-1980 | 462 |
| Per Cent Population Change, 1970-1980 | 25.36 |
| Absolute Population Change, 1980-1990 | 555 |
| Per Cent Population Change, 1980-1990 | 24.30 |
| Population Estimate, 1996 | 3025 |
| Population Estimate, 2000 | 3244 |
| Population Estimate, 2005 | 3467 |
| Population Estimate, 2010 | 3682 |
| Population Estimate, 2015 | 3884 |
| Absolute Population Change, 1990-1996 | 186 |
| Per Cent Population Change, 1990-1996 | 6.55 |
| Absolute Population Change, 1996-2005 | 442 |
| Per Cent Population Change, 1996-2005 | 14.61 |
| Absolute Population Change, 2005-2015 | 417 |
| Per Cent Population Change, 2005-2015 |