The only American Civil War landmark of any merit in Southern California was located in the Los Angeles area city of Wilmington. It was built by the U.S. Government at a cost of $1 million and was only occupied for 4 years, from 1862 to 1866. During its short years of operation, it housed over 13,000 (Not all at once). After decommissioning it became a college, but is now a historic landmark and museum. Only 2 of the 20 orginal structures still remain.
Drum Barracks Civil War Museum: 1052 N Banning Blvd. Wilmington, California.