The post office list on Jim Forte's website lists Vacation, California in Sonoma County with dates of 1904-1941
Postal Bulletin 16637, dated March 22, 1935, which triggered the collector to send for a "last day" cover":

Postal Bulletin 16650, dated April 10, 1935, reversing the order before the closure could take place, but no doubt the collector's cover was in the mail and was then serviced giving nothing more than a normal cover:

Postal Bulletin 18261, dated August 14, 1941, with closing notice which actually happened:

Vacation is directly below the second O of Sonoma with the meridian line running right through the town's location dot (from the California map in the "1920 New World Atlas" published by C.S. Hammond):

Add: Vacation, California is listed in the 1904-1910 Postal Bulletins with annual opening and closing dates as a "summer post office" and is listed in Chester M. Smith, Jr.'s article "Summer and Winter Resort Post Offices of the United States, 1891-1966" which appeared in the July 2000 American Philatelist. I am unclear about any annual cycles from 1910 to 1941 or whether is was open continuously. As Smith notes, the annual notices in the Postal Bulletins are sparse.