1. Map showing relative ease of excavation of geologic units in the Henrys Lake quadrangle, Idaho and Montana [cartographic material] Yale Public content 1972. 2013-04-04T19:50:23Z. 2013-04-10T17:34:27Z. Witkind, Irving Jerome, 1917-. U.S. Geological Survey. English. Public. Idaho, Fremont County, Montana, Madison County, Beaverhead County, and Gallatin County.