What is the name of the place where at one time almost everybody knew sign language

Answer 1

The name of the place is Martha's Vineyard. In the 18th and 19th centuries, a high prevalence of hereditary deafness on the island led to a unique sign language known as Martha's Vineyard Sign Language (MVSL). The high proportion of deaf individuals in Martha's Vineyard resulted in most community members being able to communicate using sign language, making it a place where almost everybody knew sign language.