Whittier is a city in Southern California in Los Angeles County, part of the Gateway Cities. The 14.7-square-mile (38.0 km2) city had 87,306 residents as of the 2020 United States census, an increase of 1,975 from the 2010 census figure. Whittier was incorporated in February 1898 and became a charter city in 1955. The city is named for the Quaker poet John Greenleaf Whittier and is home to Whittier College. The city is surrounded by three unincorporated areas sharing the Whittier name, West Whittier-Los Nietos, South Whittier, and East Whittier, which combined are home to a larger population than Whittier proper.

The Gateway Cities Region, or Southeast Los Angeles County, is an urbanized region located in southeastern Los Angeles County, California, between the City of Los Angeles proper, Orange County, and the Pacific Ocean. The cluster of cities has been termed "Gateway Cities" in that they serve as a "gateway" between the LA and Orange counties, with the city of Cerritos equidistant from Downtown L.A., Long Beach, and Santa Ana in Orange County. As such, the area is central to the Los Angeles-Long Beach-Anaheim, CA Metropolitan Statistical Area (MSA), and has a population of approximately 2,000,000 residents.