The University of Wyoming in Laramie has a fine collection of maps and atlases. The Wyoming State Engineer's Office at Cheyenne has a large library of technical maps.
The Family History Library has a few maps of Wyoming. These show trails, roads, forts, migration routes, and other features. Atlases that describe Wyoming's progression from Indian lands through various territorial designations are on Family History Library film 002083.
Printable maps are also available from the National Atlas of the United States -- http://nationalatlas.gov/printable.html