Los Angeles County is a county in California and is the most populous county in the US. The county seat is the city of Los Angeles. The county's population is larger than the populations of 42 states and is home to over a quarter of all California residents. Los Angeles County boasts a GDP among the twenty largest in the world. The major population centers are the Los Angeles Basin and the San Fernando and San Gabriel Valleys. The major industries are international trade, motion picture and television program production, music recording and production, aerospace, and law and medicine.