1. Colorado, Platte Canyon sheet Yale Public content 1893. 2011-05-17T19:41:53Z. 2015-10-21T14:59:23Z. Geological Survey (U.S.). The Survey. English. Public. Douglas County (Colo.), El Paso County (Colo.), Jefferson County (Colo.), Park County (Colo.), and Teller County (Colo.).