Pasayten River is a small river (more like a creek) located north of the North Cascades pass in the wilderness area. It flows into Canada. It's a long hike from anywhere. It's fished rarely by
anyone except the headwaters near Harts pass where mostly small brookies are avaliable. I think it has rainbows and also Dolly Varden in the lower reaches. I've never fished it myself and if you do you'll be one of the few who ever have.