searching for: "joseph tongue" gualala ca 1888
found a few mentions. this one says the most, but it is what you already know:
https://www.tsra.org/wp-content/uploads/2021/05/Historic-Marker-Private-Brochure.pdfthat source said he came to San Francisco in 1880 where he was naturalized, and moved to Gualala the same year.
there is a record that says he bought land in California February 26, 1880.
I don't know why familysearch dates it as 21 April 1874 on the index.
https://www.familysearch.org/ark:/61903/1:1:6NXN-ST3TSearching for him at familysearch will find a lot of voter registration information and business directory listings for the period 1880 to 1900, if you just want to fill in the timeline.
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Have you looked for Mary (McCarthy) Reynolds in 1900 to see what name she was using? I didn't find her.
She isn't with her son Vance
https://www.familysearch.org/ark:/61903/1:1:M9PP-2VTHer first husband is said to have lived until 1931, so she could have married Joseph Tongue just about anytime after Vance's birth. I didn't find a marriage record for them. There is one for her and Joseph Reynolds 30 Aug 1882 in Elmira CA.
And she is buried as Tongue
https://www.findagrave.com/memorial/236147043/mary-e-tongethe obit attached to findagrave doesn't mention any children by Joseph Tongue, just Vance and his children as mourners.
She died 8 May 1911, acc to Calif Death Index at ancestry and probably at familysearch as well. As tongue on that record also.