This territory was first settled in 1738 as Number 2, one of the towns on the state's border laid out to provide protection against Indian attacks. The town was first granted by the Massachusetts government in 1749. In 1761, residents petitioned Governor Benning Wentworth for an incorporation, which was granted the following year, to continue until 1765. The town was incorporated again in 1765, until his Majesty's pleasure be known. Governor Wentworth named the town Wilton, probably in honor of Sir Joseph Wilton, a famous English sculptor. Wilton's coach design for King George III's coronation was later used as a model for the Concord Coach.
Population change for Fitzwilliam totaled 1,363 over 56 years, from 966 in 1960 to 2,329 in 2016. The largest decennial percent change was a 41 percent increase between 1960 and 1970, and a 32 percent increase the next decade. The 2016 Census estimate for Fitzwilliam was 2,329 residents, which ranked 128th among New Hampshire's incorporated cities and towns. The town has 67.3 persons per square mile of land area (info from NHES website)