Skagit River Watershed Boundary

Seaber, P.R., Kapinos, F.P., and Knapp, G.L., 1987, Hydrologic Unit Maps: U.S. Geological Survey Water-Supply Paper 2294, 63 p.

https://www.nrcs.usda.gov/wps/portal/nrcs/main/national/water/watersheds/dataset/
The Watershed Boundary Dataset (WBD) - is a nationally consistent watershed dataset that is subdivided into 6 levels (12-digit hucs) and is available from the USGS and USDA-NRCS-National Cartographic and Geospatial Center's (NCGC). The new 8-digit WBD (130 megabytes) and the new 12-digit WBD (980 megabytes) are available as geodatabases for download, along with the metadata. The WBD contains the most current, the highest resolution and the most detailed delineation of the watershed boundaries.