Well, I found an 1870 cite at “Making of America”
Title: The New world compared with the Old,
Author: Townsend, George Alfred, 1841-1914.
Publication Info: Hartford, Conn.,, New York,: S. M. Betts & company,, J. D. Dennison; [etc., etc.], 1870.
But surprisingly it’s also about the Australian gold rush:
The progress of Melbourne is that of San Francisco. “ Some of the New South Welsh,” says Mr. Dilke, an author, “ shutting their eyes to the facts connected with the gold rush, assert so loudly that the Victorians are the refuse of California, or ‘Yankee scum,’ that when I first landed in Melbourne, I expected to find street-cars, revolvers, big hotels, and fire-clubs, euchre, caucuses, and mixed drinks.
Found an 1884 reference to the California one.
Publication Info: Overland monthly and Out West magazine. / Volume: 3, Issue: 1, Jan 1884, pp. 103-107
...the idea brought up by the word “California” was of leisurely and patriarchal Spanish sway, vast herds and feudal domains, a dreamy, pastoral life in a country of exhaustless fertility and peaceful simplicity; the still more familiar romance of the gold rush;…
At MOA Cornell I found this:
Life in the Cannibal Islands, by J. C. Bates: pp. 529-543 in:
Title: Scribners monthly, an illustrated magazine for the people. / Volume 1, Issue 5
Publisher: Scribner and son. Publication Date: March 1871
City: New York
which has this in reference to New Zealand (the writer appears to have participated in the California gold rush, but is currently talking about Dunedin):
One morning the waiter pushed aside
several dirty socks to make room for my
plate. This was the last straw. If the filthy
things had been removed from the table, I
might have stood it; but to have them by the
side of my plate was more than human nature
could stand—even while “roughing it” in the
first days of a new gold rush.
His ”a new gold rush” suggests that he’s thinking of the California event as the same sort of thing, but that still doesn’t tell us how long after 1849 the term came to be applied there.