"The Indians who occupied most of present day Los Angeles County were [after the Chumash] the wealthiest, most populous, and most powerful ethnic nationality in aboriginal southern California " according to Lowell John Bean. They spoke "one of the Cupan languages in the Takic family." These natives lived in over 50 villages, each of which held between fifty to two-hundred natives. Before the Spanish arrived in force the total population is estimated to be about 5,000. 
In the mission era, these Indians came to be called Gabrielino after the first mission established in their territory in 1771, San Gabriel Arcángel. Mission records show that natives from other tribes in the Takic family such as the Tataviam and even a few Chumash became neophytes at the two Los Angeles area missions. San Bernardino a cattle rancho in the Redlands area, operated as a sub-mission of San Gabriel between 1819-1834, and many of the neophytes there came from an ethnic nationality called Serrano (which means mountaineer or highlander in Spanish) There were also some Cahuilla neophytes. 
In the 20th century the descendants of the Gabrielino called themselves the San Gabriel Band of Mission Indians. They are normally referred to today as the Gabrielino/Tongva Indians, which was recognized as a distinct tribe by the State of California in 1994, and has been seeking federal recognition for several decades. Their official website is: http://www.tongva.com/