The Costanoan language formed one division of the Penutian linguistic stock. Costanoan speaking people lived on the California coast between San Francisco Bay and Point Sur, and inland probably to the Mount Diablo Range.
- Monterey Costanoan, from Pajaro River to Point Sur and the lower courses of the latter stream and Salinas and Carmel Rivers.
- Saclan Costanoan, between San Francisco and San Pablo Bays.
- San Francisco Costanoan, between San Francisco Bay and the Pacific Ocean.
- San Juan Bautista Costanoan, along San Benito River and San Felipe Creek.
- Santa Clara Costanoan, on Coyote and Calaveras Creeks.
- Santa Cruz Costanoan, on the coast between Pescadero and Pajaro River.
- Soledad Costanoan, on the middle course of Salinas River.
As far as Kroeber has been able to locate them, they are as follows:
- Ahala-n, south of Martinez.
- Altah-mo, on the west shore of San Francisco Bay.
- Aulin-tak, on the coast close to Santa Cruz Mission.
- Ausai-ma, on San Felipe Creek. Awas-te, near San Francisco.
- Chatu-mu, near Santa Cruz Mission.
- Hotochtak, just west of the preceding.
- Huchiu-n, northeast of Oakland.
- Huime-n, near San Pablo.
- Huris-tak, at the junction of San Felipe and San Benito Creeks.
- Imuna-kan, northeast of Salinas.
- Kakon-ta-ruk, near Point Sur.
- Kalinta-ruk, at the mouth of Salinas River.
- Kino-te, inland south of San Francisco Bay.
- Matala-n, inl and south of San Francisco Bay.
- Mus-tuk, inland east of the mouth of Salinas River.
- Mutsu-n, at San Juan. Bautista Mission.
- Olho-n, south of San Francisco.
- Orbiso-n, at San Jose Mission.
- Paisi-n, on San Benito River.
- Posol-mi, near the south end of San Francisco Bay.
- Romano-n, south of San Francisco.
- Rumse-n, on Carmel River.
- Saho-n, on Salinas River south of Salinas.
- Sakla-n, south of Martinez. Salso-n, at San Mateo.
- Sirhin-ta-ruk, on the coast north of Point Sur.
- Sokel, at Aptos, east of Santa Cruz.
- Tamie-n, on Coyote River near Santa Clara Mission.
- Tamo-tk, near Monterey.
- Tulo-mo, south of San Francisco.
- Ulis-tak, on Coyote River north of Santa Clara Mission.
- Urebure, near the west shore of San Francisco Bay.
- Wacharo-n, near Soledad Mission on Salinas River.
- Werwerse-n, inland east of San Jose.
- Wolwo-n, inland northwest of Mt. Diablo.
Kroeber (1925) estimates that there were about 7,000 Costanoan in 1770. Today there are only a few mixed-blood descend-ants remaining. The census of 1910 returned 10; that of 1930, none.