Wappo

Wappo was spoken in the Alexander and Napa valleys of northern California, the lone survivor of the small Yuki-Wappo grouping. For a California language it carried an unusually full grammar — seven cases, and a split that let non-human nouns stay uninflected for plural where human ones did not.

Laura Fish Somersal, born into it, spent decades working with the linguists Jesse Sawyer and Sandra Thompson, recording everything she could remember. When she died on 30 July 1990 the language had no fluent speakers left. Classes drawing on her recordings began in 2012; everyone in them learns it as a second language.