Matt,
Check with the CRRM library in Golden. They have all the D&RGW valuation maps for the entire system (dated 1920 and updated to at least the early 1950's). They are stored in the basement. The maps are about 3' X 5' and the scale is
1 inch = 400 feet and have detailed info on them including the dates for siding abandonments, relocations, etc. Costs are about $5.00 per sheet. When I got copies of the ROW maps for the Chama-Durango section of the mainline for the Friends of the San Juan Extension, those maps were in the same location. Hope this helps.
Bill Malin