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.

Rosamond is an unincorporated community in Kern County, California, US, near the Los Angeles county line. Rosamond is part of Greater Los Angeles and is located in the Mojave Desert just north of Lancaster and Palmdale, two of the largest cities in Antelope Valley. As of the 2010 Census, Rosamond's population was 18,150. For statistical purposes, the United States Census Bureau has defined Rosamond as a census-designated place (CDP).