Lancaster is a charter city in northern Los Angeles County, in the Antelope Valley of the western Mojave Desert in Southern California. As of the 2020 census, the population was 173,516, making Lancaster the 153rd largest city in the United States and the 30th largest in California. Lancaster is a twin city with its southern neighbor Palmdale; together, they are the principal cities within the Antelope Valley region. Lancaster is located approximately 70 miles (110 km) north (via I-5 and SR 14) of downtown Los Angeles and is near the Kern County line. It is separated from the Los Angeles Basin by the San Gabriel Mountains to the south and from Bakersfield and the San Joaquin Valley by the Tehachapi Mountains to the north. The population of Lancaster has grown from 37,000 at the time of its incorporation in 1977 to over 157,000 as of 2019.