La Mirada is a city in southeast Los Angeles County, California United States, and is one of the Gateway Cities, on the border with Orange …La Mirada is a city in southeast Los Angeles County, California United States, and is one of the Gateway Cities, on the border with Orange County. The population was 48,008 at the 2020 census. The La Mirada Theatre for the Performing Arts and the Splash! La Mirada Regional Aquatics Center are two of its major attractions. It is the home of Biola University, an evangelical Christian institution of higher education.