The wilderness is located about 12 miles ( 19 km ) northwest of Ojai in the Santa Ynez Mountains .
The wilderness is spans most of the watershed of Matilija Creek , the main tributary of the Ventura River .
The wilderness is located about 12 miles ( 19 km ) northwest of Ojai in the Santa Ynez Mountains and spans most of the watershed of Matilija Creek , the main tributary of the Ventura River .