"Central" refers to the Central Los Angeles Area Office of the California Highway Patrol Southern Division.
Some of the scenes were shot at the actual Central Los Angeles office underneath the Santa Monica Freeway. While some early episodes used the actual interior, later episodes were shot on Stage 10 at MGM Studios in Culver City, CA (now Sony Pictures Studios) where they had built as an exact replica of the building's interior. Exterior scenes were shot at the actual Central LA office in all the 6 seasons and you can actually see in the background newer vehicles acquired by the department (e.g. Moto Guzzi, Dodge St. Regis) through the years.
The original building was torn down and replaced with a newer structure in 2002.
The actual address of the building was:
777 W. Washington Blvd.
Los Angeles 90015-4113