Stevens Pass which is the former Great Northern trackage across the Cascade Range.
Stampede pass which is the former Northern Pacific trackage across the Cascade Range.
Columbia River Gorge trackage which is the former Spokane Portland and Seattle line that runs on the Washington side of the river.
All three are used. The Cascade Tunnel of Stevens Pass is tall enough to allow container traffic where as Stampede tunnel is not. Thus, the Gorge and Stevens get the majority of traffic. A dozen trains or so use Stampede, but the city of Auburn greatly opposes expansion of rail traffic. When Stampede was first opened there was an agreement to limit trains to about a dozen per day. I am not sure of the status of that agreement. However, the State of Washington wants the Stampede tunnel modernized to allow container traffic which in turn will allow port expansion in Puget Sound.