The town of Wellesley's greatest benefactor, Hunnewell built and donated the Wellesley Town Hall and Free Library building (completed 1885), along with 10 acres of adjoining parkland. The Wellesley Free Library has since moved to a new building. He was also a frequent donor, often anonymously, to many town causes. According to a resident at the time, "When leaving here for his winter home (in Boston), Mr. Hunnewell would go to our old Town Clerk, Solomon Flagg, and say to him, 'Be sure and not allow anyone to suffer during cold weather. Send them whatever they need and I will pay the bill.' Mr. Hunnewell and Mr. Flagg were the only ones that knew whose was the helping hand."