In 1926, Caltech recruited Berkeley’s Chester Stock to head vertebrate paleontology research. Stock and his students carried out landmark studies of Pleistocene fossils, particularly at the Rancho La Brea tar pits. Work in the field slowed during World War II, and with Stock’s unexpected death in 1950, large-mammal paleontology at Caltech came to an end. In 1957, the Los Angeles County Museum of Natural History purchased Caltech’s collection. This video is a production of the Caltech Archives and Special Collections.