The William Haynes House was built in the early 1850s by William Haynes (1820-1905), a ship carpenter who often worked at the George Greenman & Co. Shipyard. The small room on the left side is a later addition, and the bay window was added in the mid-1900s when the building was used as a gift shop. The William Haynes House was acquired by the Museum in 1997 and is used for offices.

This section of Mystic was named Greenmanville after the three brothers who established their shipyard here in 1837. It was an industrial village from the 1840s to the 1890s. In addition to the shipyard, the brothers built a textile mill, rented houses to workers, managed nearby farms, and operated a store. The work schedule reflected the Greenmans’ Seventh Day Baptist faith, with the Sabbath observed on Saturday.