The Family History Library has a small collection of maps for Colorado and early western territories, including a set of topographical maps for the state. The library also has city ward maps of Denver for the year 1874 (Family History Library film 1377700; fiche 6016642). A series of maps showing changes of county boundaries between 1861 and 1913 is in Colorado Maps (n.p.)
The largest collection of maps in Colorado is in the map library of the University of Colorado at Boulder. A specialized map collection for Colorado and the southern Rocky Mountain area is in Fountain Valley School's Science Department at Colorado Springs. The Denver Public Libraryand the Colorado Historical Societyalso collect maps and atlases. The Colorado Division of State Archives and Public Recordshas the incorporation filings and original plats for most towns.
Printable maps are also available from the National Atlas of the United States -- http://nationalatlas.gov/printable.html