Here is a pretty neat website... "Historical Markers Data Base"... Found it when doing some research for our local museum...
http://www.hmdb.org
It had lots of historical markers and places to go and see, just use search function (on site) to find or add any makers in your local area or places you wish to visit...
For the GPS oriented people it has "lat & lon" and can generate a GPX file for use with "Easy GPS" or similar software...
http://www.easygps.com/
Dale