HISTORICAL 



The extensive asphalt beds occurring at Rancho La Brea, on the western 

 border of the city of Los Angeles, have been known for many years as one of 

 the most interesting of the numerous bitumen deposits of the state, and have 

 attracted the attention of many investigators concerned with the geology of 

 this region. 



The earliest description of bituminous deposits in the Los Angeles region 

 known to the writer is found in the narrative of the Portola Expedition, 1 

 written in 1769. In the account of the region traversed, mention is made of 

 springs of pitch, which were observed at a stage in the journey when the 

 party must have been in the vicinity of Rancho La Brea. While it is not 

 possible to make certain of the exact location of the pitch springs described, 

 a study of the route followed gives good reason for suspecting that the locality 

 was actually Rancho La Brea. 



Tar pools in the vicinity of Los Angeles were mentioned by Blake 2 in his 

 geological report included in the Pacific Railroad Survey, though it is not 

 clear that he referred particularly to those at Rancho La Brea, Blake's state- 

 ment is as follows : 



There are several places in the vicinity of the city (Los Angeles) where bituminous or mineral 

 pitch rises from the ground in large quantities. These places are known as tar springs, or pitch 

 springs., and some of them form large ponds or lakes. One of the springs was passed on our way 

 to the city, and was near the outcrop of bituminous shale in the banks of the creek already de- 

 scribed. This spring was nothing more than an overflow of the bitumen from a small aperture 

 in the ground, around which it has spread on all sides, so that it covers a circular space about 

 30 feet in diameter. The accumulated bitumen had hardened by exposure and its outer portions 

 were mingled with sand, so that it was not easy to determine its precise limits. It formed a 

 smooth, hard surface like a pavement, but toward the center it was quite soft and semifluid, like 

 melted pitch. The central portion of the overflow was higher than its margin ; and it was evident 

 that all the hard portion had risen in a fluid state and by the heat of the sun had been gradually 

 spread out over the surface; at the same time being constantly exposed to dust, it had become 

 so thoroughly incorporated with it that the compound had all the consistency of an artificial 

 mixture. 



i Diary of Gaspar de Portola during the California Expedition of 1769-70. Edited br Donald Eugene Smith 

 and Frederick J. Teggart. Publ. Acad. Pacif. Coast Hist., vol. 1, p. 53, October, 1909.— " The 3rd (August 3. 

 1(69), we proceeded for three hours on a good road; to the right of it were extensive swamps of bitumen which 

 is called chapapote. We debated whether this substance, which flows melted from underneath the earth, could 

 occasion so many earthquakes." Also mentioned in Diary of Miguel Costanso, Portola Expedition of 1769-70 

 Edited by Frederick J. Teggart. Publ. Acad. Pacif. Coast Hist., vol. 2, p. 1S3, August. 1911. 



- Blake, W. P., Pacific Railway Reports, vol. 5, Geological Report, p. 76, 1S57. 



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