The terrain around Seattle is pretty undulating which is not ideal for railroads.  Consequently, a good amount of the track is along the shoreline where you can be guaranteed to be flat (provided you do a little work).  Mukilteo is part of the BNSF line and it runs between the houses on the hill and the water’s edge including the new ferry terminal.  There is a station there too for the commuter trains Sound Transit runs.

The majority of the traffic is freight traffic.  Double stack containers or oil tank cars are a regular feature.  I was there to look at the ferry traffic and the wildlife but, if a train is coming, I am not going to ignore it.  One came through while I was in the station while another came through a little later when I was up at the grade crossing.  For people living the US, long freight trains are not that unusual.  For friends and family in the UK, the length of a US freight train can be quite a surprise.  The leading locos can have disappeared off into the distance but the rear of the train hasn’t even come in to sight.  A curving coastline like that along Puget Sound means it is easy to be unable to see each end.