The Sedgwick Reserve lies between what were once the two largest Chumash villages in the Santa Ynez Valley: Soxtonokmu’ to the northwest and Kalawashaq’ to the south. These villages were populated during the Late Period, which began 800 years ago and ended with colonization by Mission-era settlers from 1722 to 1822. By 1822, all of the Chumash in the Santa Ynez Valley were violently removed from their villages and survivors were baptized into the Mission system. During this period and for the next 150 years, the Sedgwick Reserve was used for ranching activities, including grazing by livestock.
In 1845, the land became part of Rancho la Laguna de San Francisco, a historic Mexican land grant. The Reserve land changed hands several times over the ensuing century. Pio Pico, acting governor of the Californias, granted original ownership to Octaviano Gutierrez, a retired artillery sergeant of the Mexican army, local politician during California’s American transition, and head of a prominent Spanish family. in 1865 Gutierrez sold the land to New York-born Samual B. Brinkerhoff, Santa Barbara's primary medical doctor at the time. Later owners included Ohio industrialist Robert I. Gale who managed the ranch from his residence in Santa Barbara and continued the breakup of the original land grant. In 1948, noted rancher Evan S. Pillsbury II bought the remaining acreage for cattle grazing. The Pillsbury family was the first owner to make the ranch their primary home and was responsible for many of the infrastructural improvements we now see on the Reserve.
Philanthropist, sculptor, writer, and rancher Francis Minturn “Duke” Sedgwick and his wife, Alice de Forest Sedgwick, bought the property from Pillsbury in 1952. They moved from the nearby and smaller Rancho Corral de Quati. They ran the ranch for cattle and used it as their primary residence. Duke Sedgwick established his art studio there as well. In 1997, the land entered the Natural Reserve System (NRS) after the Sedgwicks bequeathed most of the ranch to the University of California for interdisciplinary teaching and research. The remaining portion was acquired through efforts of the Land Trust for Santa Barbara County and numerous other supporters.