Hi patrexjax:
When I was a young teenager, my mum and an Irish lady made the mistake of believing we found my ancestor's "family" in Ireland. It turned out that the "John" whom we believed to be our ancestor was not our ancestor (but he could actually be the cousin to our John). Decades later, we still do not know our connection to the Irish family, or even if there is a connection. (I hope that makes sense.)
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While there are a lot of similarities to Mr. and Mrs. Spoor's arrival in San Francisco, I can't help but wonder if he was
your W.G. Spoor.
Looking at the article in the Daily Alta California, passengers mentioned were "M Tasket, Mr and Mrs Spoor, M Martin, Mrs. Bowden and child, Miss Coghlan, Mr Turner and 14 in the steerage."
Do any of the names mean anything to you? Could he have been travelling with friends, business acquaintances, neighbours, etc.?
I believe the Captain of the Brig Onyx was Captain Nicholas Coghlan, so Miss Coghlan may have been his daughter.
...My initial "gut reaction" is that he would have stayed near the ocean as he was familiar with ships and sailing.
Unfortunately, I do not know enough about West Coast history to suggest where Mr. Spoor may have travelled next but do keep in mind that he possibly could have ventured into Canada.
Also, is there a possibility that while the Onyx sailed to San Francisco, perhaps that wasn't the last port on her voyage? Could the ship have travelled up or down the coast after arriving? Or, even sailed to Hawaii?
The article mentions Mrs. Spoor. If this was your Mr. Spoor, I wonder when and where they married?
Is there a possibility of reading the entire article from the Newcastle Journal, dated 25 October 1851? Perhaps more clues may be found in the article? [I can only find it on one of the "pay sites" and it is only a snippet.]
I think there is something more to be found and will continue to have a look around.