From Jim Forte's website, Christopher, King County, Washington operated 1887-1917.
More specifically, Postal Bulletin 2169 dated April 16, 1887, announced the establishment of Christopher, (then, still) Washington Territory on March 22, 1887, and the appointment of Thomas Christopher as postmaster.
Postal Bulletin 11461 dated Sept 28, 1917, indicated the discontinuance of Christopher effective October 15, 1917, with mail going to Auburn and records/supplies going to Seattle.
From C. S. Hammond's "1920 New World Atlas", here is King County, in West-central Washington State and a close-up from the lower left area showing Christopher just north of Auburn.

