All trains leaving Anchorage to either Whittier or Seward use the same common track
from Anchorage city limits to the Portage Junction where the two ports service diverge.
Google Map for reference: Zoooom it IN or OUT for more less detail and follow the
tracks where they go:
Google Maps
A Map is like a picture with a thousand word explanation
Basically Carnival Corp ships (Carnival Princess Holland-America) use Whittier
and the others Seward - - -
GTJ has a real good handle on the Alaska RR and cruise line operation in Alaska.
The railroad stop origin at the Anchorage AIRPORT was only a recent development
in the pass few years and creates a unique option alternative to transportation
to and from the ports in conjunction with cruise travel and airline connections.
Just remember to book as early as possible to take advantage of these arrangements !