Roger..In the past I exercised several of my 9 neurons on how to make oblique 3D views work. You have to limit the area viewed, it helps to have a reference box, and it helps to animate as you rotate around a volume. This might work for an area 50 km by 30 km by 20 km (for example) but not for all of California. I suppose you could use color for depth....and just fade out for time/date (as you originally intended to). Just do vertical map view of California/Nevada with color for depth....
Chris