La Brea is the Spanish word for the tar. The 'tar' pits were used as a source of asphalt (for use as low-grade fuel or as a waterproofing or insulator) by early settlers of the Los Angeles area. The bones were taken for the remains of unlucky pronghorns or local cattle that had become mired.
Among the prehistoric species associated with the La Brea Tar Pits are mammoths, dire wolves, cave bears, ground sloths, and the state fossil of California, the saber-toothed tiger.
Radiometric dating has given ages from preserved wood and bones of 38,000 years for the oldest known material from the La Brea seeps, and they are still ensnaring organisms today.
Rancho La Brea is the most famous, but there are two other asphalt pits with fossils in southern California: in Carpinteria, Santa Barbara County and McKittrick, in Kern County.
For other rich deposits of fossils, see Lagerstätten.