This study explores the historical distribution and abundance of anadromous steelhead and associated freshwater rainbow trout in the Santa Ynez River watershed of northern Santa Barbara and western Ventura counties, California, prior to the completion of Bradbury Dam in 1953. Steelhead and rainbow trout once occurred throughout the Santa Ynez River basin, which hosted one of the largest runs in central and Southern California. The size of the Santa Ynez River’s steelhead runs varied dramatically due to climatic and hydrologic cycles. Yet the River still supported an important recreational steelhead fishery until the early 1950s, when the population collapsed following the construction of Bradbury Dam. Few steelhead spawn in the Santa Ynez today, but the river remains a crucial site for the recovery of southern steelhead, which since 1997 have been listed as endangered under the federal Endangered Species Act.