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.
United States Census Bureau State and County Map. This map will allow you to zoom in on any state or county in the United States and read the names of all of the neighboring counties.
The Wyoming State Archives has an on-line state Historic Map Collection. The Historic Map Case Collection includes more than 12,000 over-sized maps, plans, certificates, posters, newspapers, etc of subjects ranging from Wyoming to the United States as a whole.
Printable maps are also available from the National Atlas of the United States -- http://nationalatlas.gov/printable.html