Topographic maps are free to view and download:
This site allows you to search for maps in a specific area, then view a map as an overlay. You can also download any map for free!
The United States Geological Survey (USGS) topoView site: https://ngmdb.usgs.gov/topoview/viewer/#4/40.00/-100.00
The USGS National Map: https://viewer.nationalmap.gov/basic/?basemap=b1&category=histtopo,ustopo&title=Map%20View