The Valley is home to numerous companies, the most well-known of which work in motion pictures, music recording, and television production. The former movie ranches were branches of original studios now consisting of CBS Studio Center, NBCUniversal, The Walt Disney Company (and its ABC television network), and Warner Bros.
The Valley was previously known for advances in aerospace technology and nuclear research by companies such as Lockheed, Rocketdyne and its Santa Susana Field Laboratory, Atomics International,Litton Industries, Marquardt, and TRW’s predecessor Thompson Ramo Wooldridge.
Most of the San Fernando Valley is within the jurisdiction of the city of Los Angeles, although a few other incorporated cities are located within the Valley as well: Burbank and Glendale are in the southeast corner of the Valley, Hidden Hills and Calabasas are in the southwest corner, and San Fernando, which is completely surrounded by Los Angeles, is in the northeast valley. Universal City, an enclave in the southern part of the Valley, is unincorporated land housing the Universal Studios filming lot. Mulholland Drive, which runs along the ridgeline of the Santa Monica Mountains, marks the boundary between the Valley and the communities of Hollywood and the Los Angeles Westside.