http://www.nationalatlas.gov/maplayers.html
The link above will take you to the national atlas website. The interface of the website is pretty grainy to be honest, but gives it almost an authentic feel. While toying around with the interactive site, you will find many useful tools. Everything from air pollution sites to the geography and terrain of different locations around the United States is available. You can then search different maps by category which include, map layer, printable maps, wall maps, dynamic maps and you can even generate your own map using the “map maker” tab. This link of the national atlas will keep you occupied for hours and there is a ton of very useful information within every tab and link.