* https://en.wikipedia.org/wiki/List_of_sign_languages
* https://en.wikipedia.org/wiki/List_of_sign_languages_by_numb...
Also, for the very young:
* https://en.wikipedia.org/wiki/Baby_sign_language
Wonder if it'd be easier to create a 'universal' sign language than a universal spoken one (e.g., Esperanto, or an old lingua franca like Latin).
American Sign Language (ASL) is often the second sign language non-Americans learn as it has a some international presence.
But ultimately sign language users are no more likely to decide on and widely adopt a universal language than spoken language users.
ASL is more similar to French sign language. Thanks to Thomas Gallaudet, who founded a school in 1817 in Connecticut. Gallaudet was American but studied in Europe and learned about teaching Deaf people in part from a French school.