Day to day I depend on paper maps (DeLorme and Benchmark ) while truck camping. Visiting local libraries gives great access to the internet’s warehouse of digital maps. publiclands.org is my favorite. Then I check out freecampsites. A new map, for fun places to visit, is the US Topo.
The US Topo map is fascinating. In 2009, USGS began the release of a new generation of topographic maps in electronic form, and is now complementing them with the release of high-resolution scans of more than 178,000 historical topographic maps of the United States. The surprising word is historical. You pick an area, then select the date and an old map pops up, if one exists. They also have current topographical maps.
This is a great resource for metal detecting, finding old mining towns, old train sidings, as well as areas for hiking.