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.

Los Angeles County, officially the County of Los Angeles, and sometimes abbreviated as L.A. County, is the most populous county in the United States, with 9,861,224 residents estimated in 2022. Its population is greater than that of 40 individual U.S. states. Comprising 88 incorporated cities and many unincorporated areas within a total area of 4,083 square miles (10,570 km2), it is home to more than a quarter of Californians and is one of the most ethnically diverse U.S. counties. The county's seat, Los Angeles, is the second most populous city in the United States and the most populous city in California, with 3,822,238 residents estimated in 2022. It is also known for being the home of the American film and television industry, a distinction it has held since the early 20th century which has given the county global prominence.