One of the interesting ideas (that was proposed even back when SEA was adding it's third runway) is to run high-speed rail to Moses Lake Airport in Central Wash

One of the interesting ideas (that was proposed even back when SEA was adding it's third runway) is to run high-speed rail to Moses Lake Airport in Central Washington and just expand there. That would have been an interesting idea before the railroad right-of-way was turned into a multi-use trail. There's another rail corridor that goes through Stampede Pass, but I don't know that it would be usable for "high-speed rail" (nor do I know that it even goes anywhere useful).