Additional tidbits:

The mill at Port Gamble had their own 44 tonner, visible from "Main Street", down their steep access road. Suggest visiting the town's museum; photos? Scene would make a unique model.

For the Seattle dock location, prowl E. Marginal Way South, about a half mile North of Spokane St.
Spur track, or concrete replacement, on about a 45 degree bias may be visible.
My copy of The Thomas Guide shows the carloading waterway, but no trackage west of the track closest to E. Marginal Way. By the way, this was Milwaukee and Union Pacific access to the team tracks and freight warehouses near the Alaskan Way viaduct ramps to First Avenue S. Some trackage visible. Crossed NP track from Stacy Street Yard to the Seattle Waterfront near Coast Guard Station. This last track became the Waterfront Streetcar. RIP The present walkway and jogging path was NP's route to what is now the Burke-Gillman trail, Woodinville and Canada.

Distantly related: Milwaukee served Everett via their line thru the Weyerhauser Mill at Snoqualmie, Carnation, bridge over Skykomish River, trackage rights on GN, trackage in South Everett to their freight shed; may still exist. Go to BNSF wye are wander to the south.

Milwaukee was a real retail railroad; searching for "leftovers".

Happy hunting