San Francisco's Post Office opened by March 15, 1849 and its
first postmark was a manuscript, used from March 15 to June 20.
San Francisco began using a postmarking device on June 20, the
straightline illustrated above, with the date written in
manuscript. Rates were indicated in manuscript until devices
were obtained later in 1849. In the early years, there was no
need for cancels because there were no stamps available to
cancel until the United States 1851 issue. Three useful sources
exist for classifying San Francisco postmarks, rate marks and
cancels: - The most comprehensive is Mahoney, John M., San
Francisco Postal Markings, 1847-1900, La Posta Monograph Series,
Vol. 8, La Posta Publications, Lake Oswego, Oregon, 1992.
Mahoney's book includes tracings of postmarks, killers, rate
marks and other - Also important is Williams, John H.,
California Town Postmarks, 1849 - 1935, Western Cover Society,
1997, published by Leonard H. Hartmann, Louisville, Ky. This
book deals exclusively with postmarks and contain