History of Rancho La Brea | Natural History Museum of Los Angeles

The history of fossil collecting at Rancho La Brea

Originally, Rancho La Brea was a Mexican Land Grant of over 4,400 acres given to Antonio Jose Rocha in 1828, with the proviso that the residents of the pueblo could have access to as much asphalt as they would need for personal use. As Los Angeles grew, the Rancho was eventually subdivided and developed. Its last owner was George Allan Hancock, who recognized the scientific importance of the fossils found in the asphaltic deposits. Hancock Park was created in 1916 when he donated 23 acres of the ranch to the County of Los Angeles with the stipulation that the park be preserved and the fossils properly exhibited.

The earliest written mention of the "springs of pitch" is in the diary of Juan Crespi, a Franciscan friar in 1769. He recorded the events of the expedition of Gaspar de Portola, the first Spanish Governor of the Californias, in 1769‑1770. More than a century passed before the first published mention of the occurrence of extinct fauna at Rancho La Brea was made by William Denton in 1875. Until then, the bones found associated with asphalt deposits were considered to be remains of domesticated stock or other animals of the region. However, Denton's work was soon forgotten; it was not until 1901 that the bones were (again) recognized as fossils of extinct animals by W. W. Orcutt, a prominent Los Angeles geologist. Orcutt, with fellow scientist F. M. Anderson, collected intermittently for about four years until they discovered a fossiliferous deposit that contained more bones than asphaltic matrix. Excited by this rich find, Anderson contacted J. C. Merriam at the University of California, Berkeley, in 1905. Finally, the significance of the fossil bones found at Rancho La Brea were recognized and would not be forgotten.

Between 1905 and 1915, excavation at Rancho La Brea was at its peak. Foreign and domestic institutions became interested in acquiring fossils from the area and sent individuals or crews to collect. Indeed, visiting amateurs were known to take away many souvenirs. Beginning in 1907, J. Z. Gilbert, zoology teacher at Los Angeles High School, periodically brought a work force of students to exhume specimens. Gilbert was first to create local interest and monetary support through the Southern California Academy of Sciences and the Los Angeles County Board of Supervisors, and directed the excavation of a large "Academy Pit" in 1910. This served as the nucleus of the fossil vertebrate collections at the (then) fledgling Los Angeles Museum of History, Science and Art (now the Natural History Museum of Los Angeles County). Merriam finally secured funds in 1912 for the first large-scale excavations and the University of California excavations yielded thousands of specimens. G. Allan Hancock feared that the collections would be scattered and taken from the community, so in 1913 he gave Los Angeles County the exclusive right to excavate for a two-year period. The largest and best documented collections at that time were made by the Los Angeles Museum between 1913 and 1915. During this period, 96 sites were excavated yielding well over 750,000 specimens of plants and animals. After Hancock Park was established in 1916, little in the way of formal excavation was accomplished until 1969. Intermittent small-scale excavations between 1929 and 1931 stopped when museum field parties were sent to work in New Mexico. In 1945, systematic coring was undertaken to locate more fossiliferous sites within the park. Ultimately, a project designed to intensely sample and collect data was instituted by the Natural History Museum in 1969 which continued until 2007, when planning for work on Project 23 commenced.

In the 55 years following the early collecting activities, excavation and data gathering techniques had changed and improved, and the science of paleontology had evolved in its ability to extract knowledge from data and specimens neither noted nor collected by the early excavators. Early collectors concentrated their efforts on the remains of the larger, more spectacular plants and animals and rarely noticed or collected those of smaller organisms. In addition, important information pertaining to geology and specimen orientation was not recorded. To help rectify these collecting biases, the Rancho La Brea Project began on June 13, 1969. It was decided to reopen a major deposit of fossils–Pit 91–that had been excavated to a depth of 10 feet in 1915, but then left in order to use it as a permanent exhibit. Later, the proposed exhibit–the Observation Pit–was moved to its present, more favorable, location. Newly developed techniques, in concurrence with established paleontological and archaeological methods, were employed to intensely sample and carefully record biologic and geologic data in the renewed excavation.

When the foundation for the Page Museum was excavated in 1975, a unique, laterally extensive, deposit was discovered which contained the largest concentration of articulated and associated specimens ever collected from Rancho La Brea. With the cooperation of the contractors, 20 blocks of bone, plant and matrix were carefully salvaged so that none of the associations and articulations would be lost in the removal process. The fossils preserved in these blocks will provide detailed anatomical information about the extinct animals and insights into their Late Pleistocene ecology. 

Early in 2006 the Los Angeles County Museum of Art began construction of an underground parking garage on the west end of Hancock Park. Within the confines of the future structure (~100,000 sq. ft.), 16 previously unknown asphaltic fossil deposits were discovered along with the skeleton of a near-complete Columbian mammoth. In order to hasten construction, the 16 deposits were boxed into 23 large “tree-boxes” and crated to a safe location within Hancock Park. The mammoth skeleton was mapped, plaster-jacketed, and excavated and brought to the Page Museum. Since the summer of 2008 the Page Museum has been excavating the boxes and preparing the mammoth material. Dubbed Project 23, this salvage effort has been estimated to double the size of the present collection.

In recent years, subsurface testing and excavations for developments in and around Hancock Park have considerably augmented previously available stratigraphic information. A re‑evaluation of information recorded during the early days of excavation, coupled with data now available, provide the basis for understanding the mode of accumulation of these Late Pleistocene deposits.

Summary of important dates and people

• 1875 W. Denton first describes fossils from Rancho La Brea
• 1901 W. W. Orcutt and F. Anderson excavate at Rancho La Brea
• 1905 J. C. Merriam at Berkeley recognizes the importance and comes to excavate
• 1907 J. Z. Gilbert LA High School brings studenst to excavate
• 1910 J. Z. Gilbert opened ‘Academy’ pit with funding from Southern Californian Academy of Sciences
• 1913 Hancock owner of the ranch gives exclusive rights to Los Angeles County to dig
• 1913-1915 are the best documented excavations by the museum and yields 750,000 specimens in 96 sites
• 1916 Hancock Park designated as a protected park and donated to Los Angeles County
• 1929-1931 Bliss and others occasionally excavate for the museum
• 1945 core samples taken around the park to look for more sites
• 1963 Rancho La Brea is designated a National Natural Landmark by the National Park Service
• 1969 Pit 91 is reopened in order to collect intense samples due to original collecting biases (left at 10 ft. in 1915)
• 1969-2007 Pit 91 intensely sampled
• 1975 Page Museum Salvage: lateral extensive deposit with largest concentration of articulated specimens ever found at Rancho La Brea
• 1985 Salvage of Los Angeles County Museum of Art's Japanese Pavilion site and the Hancock Family dump site
• 2008 Project 23 salvage begins to excavate 23 tree boxes and prepare a near-complete mammoth