Tamcan

Tamcan or Tammukan was a local tribe of Delta Yokuts-speaking natives in the U.S. that once lived on the lower reaches of California's San Joaquin River in what is now eastern Contra Costa County and western San Joaquin County, California. The Tamcans were absorbed into the system of the Spanish missions in California in the early nineteenth century; they moved to Mission San José, near the shore of San Francisco Bay, between 1806 and 1811. At the mission, they and their descendants intermarried with speakers of the San Francisco Bay Ohlone, Plains Miwok, and Patwin Indian languages. Mission Indian survivors of these mixed groups gathered at Alisal, near Pleasanton in Contra Costa County, in the late nineteenth century.

It has been stated that Tammukan was a specific place, a lost city even. It is not known how that idea came about. However, Father Narciso Duran did use specific place markers for "Tamcan" and other "rancherias [communities]" along the San Joaquin River on his 1824 map of the native communities east of Mission San Jose.