On the right side of Conzelman Road, note the buildings set into the side of the hill.
Mine depot building #411 pictured here was one of two buildings where ammunition was stored. During World War II, remotely-controlled mines were being laid under San Francisco Bay, with Fort Baker at the center of the effort.
It's difficult to see in this small image, but there's a faded "No Smoking" sign still posted above the door . . . for obvious reasons.