Gill served an apparently undistinguished term as acting governor until his own death in 1800, ten days before his successor, Caleb Strong, assumed office.

Gill was a significant benefactor and founder of Leicester Academy, and supported the congregational church in Princeton, where the family had a large estate.

Upon her father's death the couple inherited Prince's lands in western Worcester County, one of the largest tracts in what became the town of Princeton.

[9] When the American Revolutionary War broke in April 1775, Gill became involved in the early military organization of the Siege of Boston, heading the provincial congress' supply committee.

[12] In this role he sat on the panel that heard the preliminary cases in 1781 involving Quock Walker, an African American seeking a declaration of his freedom.

Gill's panel decided in Walker's favor, and the Massachusetts Supreme Judicial Court eventually confirmed the judgments on appeal, declaring that slavery was incompatible with the state constitution.

[9] After the death of the immensely popular Governor John Hancock in 1793, the state's gubernatorial election of 1794 was a wide open race.

Although Gill polled well in Boston and the eastern counties (present-day Maine), the Federalists won a decisive victory over the divided opposition.

[16] Gill's politics are unclear: historian Anson Morse is of the opinion that his popularity was not sufficient to head the ticket of either the Federalists or the Democratic-Republicans.

[17] Historian John Barry observes that Gill's term as acting governor, even though it was for essentially a full year, was "too short to be particularly distinguished".

Sumner finally took the oath of office in early June, but died a few days later, at which point Gill became acting governor.