Genealogists need maps to oragnize information geographically, know where to look for records, and have an idea of how their ancestor's residences fit into the larger area as a whole.
One key is that the maps be contemporary to when your ancestor lived in the area. Modern maps can be helpful in finding current locations of cemeteries, but many other times our research requires contemporary maps.
If you are stuck on a forebear, get a contemporary map of his or her area. Perhaps that map is just the one you need to get your around or over that brick wall.