If I wanted to goto CA from PA, would I need to route from the state furthest west on the east disc and then reroute using the west disc? Thanks.

Yes, I believe that you do. I had the D1 several months. The states in the middle (CO, NE, IA, etc.) overlap on the two sets of discs.

Put the west coast disc in and set your destination. Once it's set put your east coast disc back in and be ready to swap discs once you get to where they crossover.

Awesome, thanks for the quick responses, keep on rocking.