When the Taiping rebellion against the Manchu Dynasty broke out in China in 1851, Chinese workers streamed to Gum San ("Gold Mountain"), their name for California. In their packs and pockets the men brought Chinese coins that are now found commonly in the excavations of their California settlements and work areas.

The Yema-po excavations yielded 26 Asian coins. These coins provide insights into at least three aspects of life at Yema-po and in late nineteenth century China:
The chronology of the coins
Where the coins were minted
The probable uses of the coins at Yema-po

Miller, George R., Lyssa Stapleton, Martha Barnes and Sabina Morganti
  1998  The Coins and Gambling Tokens. In Yema-po: The Overseas Chinese
 and the Construction of the San Leandro Dam, edited by George R. Miller.
        C.E. Smith Occasional Paper in Anthropology, No. 2.  California State
   University, Hayward.