Couldn't they simply incorporate?, in the municipal sense.
A quick search indicates this is the process in California:
> Today, incorporation means going through a rigorous and complicated process with the Local Agency Formation Commission (LAFCO) in the county where the community sits (each census-designated place must be contained within a single county). Before a community can even apply for incorporation, at least 25 percent of registered voters there (a community must have a minimum of 500 registered voters to qualify at all) must sign a petition stating their desire to make their community a city.
A quick search indicates this is the process in California:
> Today, incorporation means going through a rigorous and complicated process with the Local Agency Formation Commission (LAFCO) in the county where the community sits (each census-designated place must be contained within a single county). Before a community can even apply for incorporation, at least 25 percent of registered voters there (a community must have a minimum of 500 registered voters to qualify at all) must sign a petition stating their desire to make their community a city.
https://californialocal.com/localnews/statewide/ca/article/s...