Context: I have only had two meetings thus far on iTalki with different instructors each time, neither of which are themselves deaf. Therefore, the information provided in this post is from a secondary source I found in my research on the topic rather than via interview.
This video is about the history of a sign language in the continental US other than standard American Sign Language in use today. The interview focuses on Plans Sign Language or Hand Speak in the Midwest. Hand Speak was a lingua franca used among Indigenous Americans in the Midwest prior to colonization. Several known signs were lost over time as the settlers colonized their land and prevented the passing on of Native knowledge Today, there are a limited number of fluent signers, and they fill the gaps in their lexicon with ASL.
I think it is very important that this knowledge is preserved for the next generation in order to revive the culture threatened by US imperialism. It is also important to teach hearing and deaf signers alike the history of sign languages in America. Along with common home signs, there are at least four recognized dialects of ASL: American Sign Language, Black American Sign Language, Martha's Vinyard Sign Language, and Plains Sign Language. Each of these languages developed from a community's unique intersectional struggles, particularly with otism and race.
Furthermore, I feel that many people come into ASL classrooms expecting to learn a universal sign language, the deaf equivalent of Esperanto. This is simply not the case. Just as languages developed around the world over thousands of years, so have ways to communicate between deaf and hearing individuals. Yes, the standarization of various sign languages is a recent developement closing the gap between many signing communities, however sign language in the US is still totally different from sign language British Isles even though both countries have English as the dominant language! In fact, someone who knows ASL would likely have an easier time understanding LSF (French Sign Language) because that was the basis for developing ASL.