A Search Engine for US Maps Made Using Google

This is a twofer that I got from Larry Ferlazzo's G+ tonight. The best part is that it has a search engine for Google maps.   Type in any subject into the search engine, US or foreign and you will get Google maps (such as the civil war ones below) on any topic.  Alternatively you can hit on the red lettered "history engine" and search through American maps collected by the University of Richmond.