The Thomaston Historical Society is housed in the only remaining building of the original General Henry Knox estate. Built between 1793 and 1795, it was one of seven out-buildings which stood in a semicircle behind the original Knox mansion named Montpelier. Called the "Farmhouse" or the "tenants' building" it served as a living facility for the unmarried men employed on the estate to care for the animals, do the farm chores and maintain the residence. The structure is a two story Federal style brick building with center chimney and exposed beams.

After the original mansion was razed to make way for the Knox and Lincoln Railroad, the building was kept and put to use as the Thomaston Railroad Station. It served in that capacity from 1872 until the railroad went out of business in 1956. After being purchased by the D.A.R., the building was given to the Knox Memorial Association which eventually turned it over to the Thomaston Historical Society in 1972 . Restored for use by the Society, the first floor area now has a large meeting room with a small kitchen, rest room and archival storage room and display areas, the upper floor houses the Society's museum and a book depository for the many publications written for and sold by the Society. In 1974 the building was placed on the National Register of Historic Places.