1. Colorado, Leadville sheet Yale Public content 1891. 2011-05-17T18:29:36Z. 2015-10-21T14:59:21Z. Geological Survey (U.S.). The Survey. English. Public. Chaffee County (Colo.), Eagle County (Colo.), Lake County (Colo.), Park County (Colo.), Pitkin County (Colo.), and Summit County (Colo.).