Geologic Map of the Yellowstone Volcanic Field
Download the GIS file from the USGS here
Data is in the UTM Zone 12N Projection with the NAD27 Datum.
Christiansen, R.L., 2001, The Quaternary and Pliocene Yellowstone Plateau Volcanic field of Wyoming, Idaho, and Montana, U.S. Geological Survey Professional Paper 729-G, 145 p., 3 plates, scale 1:125,000.
Download the PDF here