The 42nd district is located entirely within Los Angeles County, and is centered around Long Beach and its surrounding suburbs.

As of the 2020 redistricting, California's 42nd congressional district has been geographically shifted to the South Bay region of Los Angeles County.

This district also takes in 2 of the Channel Islands, Santa Catalina and San Clemente, in the Southern California Bight.

The 42nd and 44th are partitioned by S Alameda St, Southern Pacific Railroad, Ardmore Ave, Long Beach Blvd, Pacific Blvd, Cudahy St, 2622 Cudahy St-3211 Santa Ana St, Santa Ana St, Salt Lake Ave, Patata St, 7038 Dinwiddie St-10112 Karmont Ave, Imperial Highway, Old River School Rd, Union Pacific Railroad, Gardendale St, Century Blvd, Highway 19.

The 42nd district takes in the cities of Huntington Park, Bell, Bell Gardens, Maywood, Signal Hill, Vernon, Cudahy, Commerce, south Long Beach, east side Lakewood, most of Downey and Bellflower, and the census-designated places Florence-Graham and Walnut Park 1972 • 1974 • 1976 • 1978 • 1980 • 1982 • 1984 • 1986 • 1988 • 1990 • 1992 • 1994 • 1996 • 1998 • 1999 (Special) • 2000 • 2002 • 2004 • 2006 • 2008 • 2010 • 2012 • 2014 • 2016 • 2018 • 2020 • 2022 From 2003 to 2013, the district covered parts of Los Angeles, Orange, and San Bernardino counties in Southern California.