Some old Metskers, USFS and USGS maps will show the old sheep trails. Some old trails may not show, and some old maps may not show them all.
They were everywhere BITD. Look at "Routes and Rocks, Hikers Guide to the North Cascades from Glacier Peak to Lake Chelan" by Dwight Crowder and Roland Tabor from 1965. Route upon route was based on the old sheep trails. I remember my first trip to Buck Creek Pass in 1972, we found a old sheep herders cabins, and there were multiple short cuts straight up and down the hill.
I really haven't noticed many outside the Suiattle and Chiwawa drainages in designated Wilderness, it sure seems like the Pasayten would have been prime.