The Karkin people lived in the Carquinez Strait region in the northeast portion of the San Francisco Bay estuary. The spoke the Karkin language, the only documentation is a single vocabulary obtained by linguist-missionary Felipe Arroyo de la Cuesta at Mission Dolores in 1821. Although meager, the records of Karkin show that it constituted a distinct branch of Costanoan, strikingly different from the neighboring Chochenyo Ohlone language and other Ohlone languages spoken farther south. Karkin has probably not been spoken since the 19th century.
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Callaghan, Catherine A. 1997. "Evidence for Yok-Utian." International Journal of American Linguistics 63:18–64.
Golla, Victor. 2007. "Linguistic Prehistory." California Prehistory: Colonization, Culture, and Complexity. Terry L. Jones and Kathryn A. Klar, eds., pp. 71–82. New York: Altamira Press. ISBN 978-0-7591-0872-1.
Milliken, Randall T. 1995. A Time of Little Choice: The Disintegration of Tribal Culture in the San Francisco Bay Region, 1769–1810. Menlo Park, CA: Ballena Press.
Milliken, Randall T. 2008. Native Americans at Mission San Jose. Banning, CA: Malki-Ballena Press. ISBN 978-0-87919-147-4.