>>1385084I usually get on
https://caltopo.com/map.html#ll=48.07458,-121.16703&z=12&b=mbt and change to the Mapbuilder Topo overlay and just look for trails that way. I backpack 40-60 miles a weekend, so sometimes it gets difficult to string enough trails together, but it can be done up here in Washington. I'd recommend starting there, then if the trail is in a certain national or state park, find the permits you need there.
The backpacking trips I've done this year all done with this method:
https://caltopo.com/m/3P3K 