A couple of summers ago I volunteered as an Interpretive Ranger on a portion of Amtrak's Empire Builder Route from Seattle to mid-Montana and back (
NPS Trails & Rails Program). Some of the most beautiful country I've ever seen is on that route west of the Cascade Mountains, between Monroe, WA and the train tunnel under Stevens Pass.
This line was part of the old Great Northern Railway, now owned and operated by BNSF, and used by both freight and passenger trains. It roughly parallels both US-Hwy 2 and the Skykomish River and runs through the Mt. Baker-Snoqualmie National Forest. There is a pay NSF campground right on the rail line called Money Creek (
http://www.fs.usda.gov/recarea/mbs/recreation/camping-cabins/recarea/?recid=17930&actid=29). But, there's dispersed camping available too (
http://www.fs.usda.gov/activity/mbs/recreation/camping-cabins/?recid=17520&actid=34).
I especially love the area where the rail line does a switchback along the Foss River at its confluence with the Tye River (where they join to become the Skykomish River) a little west of the tunnel and adjacent to the Alpine Lakes Wilderness Area. If I had a 4WD high-clearance vehicle, I'd head to where the town of Scenic use to be, off of FS-840.
To check out the FS roads in the area, the MVUM for the Skykomish Ranger District is at
http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5370908.pdf.
Hope this helps you and any other railfans that venture into Washington State.
Suanne ... who wants Toyota to make a hybrid 4WD high-clearance minivan