|Butte Special USGS 1910 - 1:15,000|
From the University of Texas Perry Castaneda Library Map Collection (link.) This map of Butte from 1915 must be pretty near the peak of underground copper mining. I have seen this map in person at the UCLA map library, so I know they have a copy. You can save the maps as JPEGs from the site, and can enlarge with a viewer, see screen print below. Thank you University of Texas!