Newcastle Ca. As the railroad leaves Rocklin headed east, the Sierras stop being a legal entity for bond purposes and start being actual mountains. At Newcastle, we see the steeper approach of track 1 vs. the longer approach track 2 took. Mainstreet Newcastle is a series of former packing sheds perched on a hilltop overlooking the surrounding area. The railroad runs atop the hill, crosses I80 and through a tunnel as it moves up to Auburn.