San Dimas Experimental Forest (SDEF)
The San Dimas Experimental Forest is a protected field laboratory under the joint management of Pacific Southwest Research Station and the Angeles National Forest, for studies of hydrology, fire, and other topics relating to the ecology of chaparral and related ecosystems.
Early history of the area now comprising the SDEF includes the presence of Native Americans, namely, the Gabrielino or Tungva Indians. Although no evidence has been found on site, they probably hunted animals and harvested acorns and other foodstuffs in the oak woodlands and other productive areas in the Forest.
Beginning in the 1700s, the Spanish Ranchos were established in the Los Angeles basin below, and hunting trips for deer, mountain lions, and bear are documented by the Spaniards. The California grizzly bear inhabited the foothills and valleys at this time. In the 1800s, gold miners, hunters, and trappers came into the San Gabriel Mountains and foothills, and many trails were built. Homesteaders occupied some of the lower ends of Big Dalton and San Dimas Canyons, and measures by local communities to control floods occurred in the late 1800s and early 1900s.
In the 1920s, Los Angeles County Forester Stuart B. Flintham was very instrumental in early reforestation and conservation efforts in the San Gabriel Mountains. Spence Turner became L.A. County Forester after Flintham's death in 1925, and established an experimental tree nursery at Tanbark Flats in 1926. L.A. County constructed a dirt road the entire way to Tanbark Flats, up the San Dimas West Fork, in 1928-29. Prior to that, only mule and hiking trails led to the Tanbark area. The Flintham Memorial was established in the West Fork of San Dimas Canyon, in honor of his early reforestation efforts.
Herbert S. Gilman, an engineer from the San Dimas Water Company, and William A. Johnstone, of the California State Water Commission, both conservationists, helped to establish the SDEF. Gilman and Johnstone were later honored for their "pioneering" efforts: in 1940 San Dimas Peak, the highest point between San Dimas and Dalton Canyons, was renamed Johnstone Peak; and in 1943 a beautiful grove of Deodar cedars at Tanbark Flats was dedicated as the Gilman Grove and a stone marker was erected in Gilman's memory.
The SDEF was officially established in January of 1933, and was formally dedicated on June 15, 1935 by the U.S.D.A. Forest Service, California Forest and Range Experiment Station (now known as the Pacific Southwest Research Station). J. Donald Sinclair was scientist in charge, and would help to guide the SDEF through its first 25 years.
In addition to the SERA (State Emergency Relief Administration), CCC (Civilian Conservation Corps), and WPA (Works Progress Administration) program workers in the 1930s, the "CO's" or Conscientious Objectors of the 1940s performed invaluable construction and research work in the Experimental Forest.
This information is from John Robinson's "The San Dimas Experimental Forest" and "History of the Dalton and San Dimas Watershed," which were originally published in the Mt. San Antonio Historian, Volume 16, No. 3.