The USGS now provides regularly updated US Topo free online topoographic maps. These maps are not as detailed as the older paper maps, but new layers are being added on a periodic basis. (HINT: For the exact name of the corresponding older paper map, search for a specific location, and then click the red marker for the name of the earlier paper quadrangle map.)
Historical Note: Recent USGS digital US Topo 1:24,000 topo maps based on the National Map omit several important geographic details that were featured in the original USGS topographic map series (1945-1992). Examples of omitted details and features include power transmission lines, telephone lines, railroads, recreational trails, pipelines, survey marks, and buildings. For many of these feature classes, the USGS is working with other agencies to develop data or adapt existing data on missing details that will be included in The National Map and to US Topo. In other areas USGS digital map revisions may omit geographic features such as ruins, mine locations, springs, wells, and even trails in an effort to protect natural resources and the public at large, or because such features are not present in any public domain database. See the recent update summary.
The Geographic Names Information System (GNIS) can also be used to identify the name of the appropriate topographic map.
Using the Search Topographic Map Cells option, select the "Search Topographic Map/Digital Product Cells" option on the far right ... then enter the place name of interest in the Feature Name field and select the state with the pull-down menu. Look for the Cell Name (name of the quad map) that has a Cell Size of "7.5 X 7.5 Minute". See the video of searching for a place name.