This page from Wilderness Connect of the Univerity of Montana has visitor information and links to high-quality interactive maps.
The United States Congress designated the Mount Baker Wilderness in 1984 and it now has a total of 119,966 acres.
https://umontana.maps.arcgis.com/apps/webappviewer/index.html?id=a415bca07f0a4bee9f0e894b0db5c3b6&find=Mount%20Baker%20Wilderness