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Steamship letters were defined by the Post Office as letters which entered the United States on Steamers under contract to carry mail for the United States. The steamship rates in effect when these markings were introduced in 1863 were 10 cents if the distance carried from the mailing office was less than 2,500 miles and 20 cents if over that distance. On July 1, 1864 the “blanket” steamship rate of 10 cents went into effect. This rate was applied regardless of distance carried from entry port. All mail arriving from non-contract vessels was to be treated as ship letter mail and subject to different rates.
These four markings were used on mail that arrived in San Francisco from steamships of the Pacific Mail Steamship Company. This company had a contract with the United States Post Office to carry mail and all such letters received should have been treated as steamship letters and subject to steamship rates. From the known usage's it appears that markings were applied specifically to mail bagged at each of the various ports of call of the Pacific Mail Steamers. Separate bags of mail were delivered to the steamer at Panama, and the Mexican ports of Acapulco, Manzanillo and Mazatlan (see map on following page). Mail from all of these locations was subject to the same steamship rates, regardless of origin. However, the frequent errors of rating, especially in 1863 and 1864, are evidence that the Postmaster at San Francisco did not understand the somewhat confusing postal regulations. The quantity of mail picked up at Panama, and hence receiving the “Steam Panama” handstamp, was far larger than that picked up at the Mexican ports. Panama served as the transfer point for mails from a wide variety of Central and South American countries. Mail arrangements for getting mail to Panama varied. |
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