The Society has a varied collection located in four buildings, three of which are on the National Register of Historic Places. The extensive archives range from historic photographs to documentary records, deeds, postcards, maps, books, and genealogical history. The Society's collection also includes 19th century furniture and decorative arts, historic textiles, ephemera capturing Cohasset's theatrical past and a large collection of paintings depicting the town's seascapes, landscapes, people and places.


The Helen Howes Vosoff Theater Archive, established in the 1980s, spans more than a century of Cohasset's theatrical history. This includes artifacts from the Hanlon Brothers' Pantomime Theater of the late 1880s, the Cohasset Dramatic Club founded in 1921 which continues performances to this day, the South Shore Players of the 1930s and 1940s and the South Shore Music Circus which began in 1951 and is a lineal descendant of the South Shore Players.


The Society's textile collection began in the 1940s and now contains close to 4,000 items. The collection covers a broad range of women's, men's and children's clothing dating roughly from the early 1800s to the present day. Exquisite wedding dresses and extraordinary quilts and samplers are among the high points of the collection.