According to the U.S. Department of Homeland Security (DHS), an estimated 2,830,000 unlawful immigrants resided in California in 2012, compared to 1.5 million in 1990 and 2.5 million in 2000. This number represents 24.7 percent of the entire estimated unlawful immigrant population in the United States (11.4 million in 2012). This estimate puts the percentage of California's population that are unlawful immigrants to be about 7.5 percent, with a majority (about 60 percent) being from Mexico. Across the entire United States, an estimated 6.8 million unlawful immigrants were from Mexico, up from 4.7 million in 2000.
More recently, the Public Policy Institute of California, estimated that, in 2013, 2.67 million unlawful immigrants resided in California or about 6% of the state's population. This is believed to be almost a quarter of all unauthorized immigrants living in the United States. Mostly, this population is from Latin American (estimated at 79%) with a declining majority from Mexico (52%). About a tenth of the state's workforce is composed of unlawful immigrants and about 13% of California K-12 school children have an unlawful immigrant parent.
DHS does not offer unauthorized immigrant estimates for Los Angeles County, but the Migration Policy Institute estimates that, at 1,062,000 persons, Los Angeles County has the largest unauthorized immigrant population not only in California, but in the nation (followed by second-place Harris County, Texas, at 373,000). Of these, 367,000 were eligible for the Deferred Action for Parents of Americans and Lawful Permanent Residents (DAPA) Program. The unauthorized immigrant population in Los Angeles County is most concentrated in the southeast county, the eastern San Fernando Valley and the San Gabriel Valley. According to a 2013 report from the University of Southern California Center for the Study of Immigrant Integration, Los Angeles has the higher percentage of self-employed unauthorized immigrants (14%) and some of the most settled in the state with a median time of residence of 10 years.
* Per the U.S. Department of Homeland Security, "Unauthorized immigrant" is defined as a foreign-born non-citizen who is not a legal resident. Most unauthorized immigrants either entered the United States without being inspected at the United States border or were admitted temporarily and stayed past the date they were required to leave. Other terms commonly used in public discourse are "illegal immigrant," "illegal alien," "unlawful immigrant" or "undocumented immigrant."
Immigration has long been a hot issue in California, even as far back as the latter days of California's Mexican period (1822 to 1846). Pio Pico, the last Mexican governor of California, lamented, "We find ourselves suddenly threatened by hordes of Yankee immigrants...whose progress we cannot arrest."