aerospace research center. When someone asks if I want to walk dogs together at JPL I am not confused. I know they don't expect to wander among research labs and allow the dogs to pee on the telescopes. They mean Hahamongna Watershed Park.
Can you blame us? JPL is so much easier to say.
The reason for the nickname is obvious if you look at a map. The real JPL (NASA's Jet Propulsion Lab) sits perched sideways atop Hahamongna rather like a jaunty beret. And calling the park JPL isn't wrong; some of the earliest rocket experiments were launched there and even later ones have been tried on its sandy acres.
This view is closer to the Devil's Gate Dam than to NASA's JPL. The dam is close to the bottom of your map view, near the 210 freeway. (You can see it if you use the zoom in satellite view.) You can't see where I took this photo; it's off to the right, under cover of trees. But the Google shot of the dam looks relatively recent.