It's neither an ex-Milwaukee Road branch or main line -- it's the former Northern Pacific Sumas Line from Renton to Woodinville, then north to Sedro Woolley and on to Sumas at the Canadian border. The only railroad to serve Woodinville was the NP, with one route coming east that traveled around the northern edge of Lake Washington from Interbay Yard, and the Sumas Line from the north and south.
The Milwaukee Road came into Renton from Cedar Falls and then to Black River Junction, from where it could access Union Station in Tacoma and Union Station in Seattle via rails it shared with the Union Pacific.
The Milwaukee Road did operate a series of branch lines out of Bellingham. Before the BN merger in 1970, the Milwaukee had to move cars between Seattle and Bellingham via car floats. After the merger, it gained trackage rights from Monroe to Bellingham on the former NP route. Milwaukee Road trains traveled on their own rails between Monroe and Cedar Falls, passing through Snoqualmie and Duvall.
The odd-looking cars you see are probably brown-colored, shed-shaped objects. They carry fuselage components for Boeing's plants in Renton and Everett.
Most locomotives on the Wilburton line (the large trestle just east of Interstate 405 is the Wilburton Trestle) now are probably GP38s, GP39Ms, or GP39Es.
Years ago, when Bellevue was a just small town on the eastern shore of Lake Washington, the trestle was sort of in the middle of nowhere.
The "Spirit of Washington" began operating on the line in 1992, if I recall.
Hope this helps,
Paul Schmidt
Contributing Editor
Trains.com
