LA-88 was one of the few dozen Nike missile bases located around LA to protect the civilian population and military industrial sites from Soviet attack and was in operation from 1957-1974. In order to protect this vital arsenal, the Los Angeles area air defense system became the first in the nation to use Army sentry dogs to protect missile sites. In November 1958, four sentry dogs and their handlers began patrolling the Chatsworth missile launch site.
It is now owned by the CA Civilian Conservation Corps. Although long removed from its original purpose, much remains intact and can be seen from the road. Many buildings are still standing, and one of the covers of the missile silo is opened.
The place is gated off, but is said to be popular with urban explorers.
UPDATE AS OF 7/16/2012: The structure shown in the picture is still there, but hollowed out. Much of the place was heavily damaged by a massive wildfire back in 2008. There's now a few buses there (all badly damaged and with bullet holes!) and you can find shells on the ground. After some research, it seems to be a training ground for the SWAT team. Plus, there's a military dog kennel.
Obscura Day location: April 9, 2011.