I'm not much of a railroad photographer, but I went out this weekend with my CoolPix and scouted out a few potential photo locations around Seattle. Here's my quick report on what's available heading north from King Street Station.
At the north end of downtown there is the Seattle Art Museum Sculpture Park that has a bridge over the BNSF mainline. The Sculpture Park leads into Myrtle Edwards Park, which runs along the BNSF mainline next to Elliot Bay. The Port of Seattle grain terminal is located next to Myrtle Edwards Park and just past the grain terminal sits the Amgen Campus, which includes the very modern Amgen Helix Bridge, which serves as a pedestrian overpass back to Elliot Avenue. Along Elliot Avenue there are several viewpoints of the railroad tracks--some of which contain some very modern sculptural and architecture backdrops. From a location on Elliot Avenue, in the space of about 30 minutes, I watched a Boeing 737 fuselage train roll by, a Talgo trainset from Vancouver, a grain train and several Washington State Ferries passed in the background. The grain terminal operations are within view and if it had been a clear day (don't I wish), the backdrop would have been the Olympic Mountains.
Further north of the grain terminal area, at the north end of Myrtle Edwards Park, there is a pedestrian/bike path that runs next to the mainline up to BNSF's Interbay Yard. Interbay is a good hike from downtown Seattle, but there are buses running every 10 minutes back to downtown.
I scouted the Ballard Locks area for shots that would include an Olympic Mountain backdrop, and I have to say that there are many good shots available at the Locks, especially of the bascule bridge that crosses the Ship Canal, but it will be difficult to include the Olympics in the background.
Golden Gardens and Carkeek Park are well known location for shooting trains, sunsets and the mountains. Metro Route 46 runs directly to Golden Gardens, Route 28 goes to Carkeek, but you will need to hike about 1 mile to get to the shoreline.
Richmond Beach is another good location for shooting, ride Metro Route 348 (from the Northgate TC) to the end of the line.
Downtown Edmonds has a WA St Ferry terminal and north of the terminal there is a beach that is accessible to photographers. Getting to the Edmonds ferry terminal is easy via Sounder (weekday afternoons only), but getting back to downtown Seattle will require several bus rides.
A very good location that requires a car is Picnic Point in Snohomish County. The train tracks curve along the waterfront, there is a bridge from the park to the beach and if the tide is out, you can walk north from the park and see an old wooden ship that ran aground decades ago and has been sitting next to the shoreline (and railroad tracks) ever since.
The last location I scouted was the Mukilteo Ferry Terminal area. Community Transit Rt 113 from Lynnwood P & R serves Mukilteo. Similar to Edmonds, the Mukilteo ferry terminal area is near the railroad tracks and it features Olympic Mountain backdrops when the weather is clear.