Sandy River Valley Sign Language

Sandy River Valley Sign Language was a village [sign language] of the 19th-century Sandy [River (Kennebec River)|Sandy River Valley] in Maine. Together with the more famous Martha's Vineyard Sign Language and Henniker Sign Language, it was one of three local languages which formed the basis of American Sign Language.
The deaf communities in the valley developed in some of the thirty villages founded by settlers from Martha's Vineyard. However, it is not clear whether MVSL itself was transmitted, or if the chain was broken and a new sign language was created once a substantial deaf population was established.