We have created several Google Maps with markers giving historic sites on them.
You can see them at the links below
Polk County Historical Markers In the mid 1980s 400 wooden markers were placed at historic sites in Polk County. A map with 380 of them was created. Many if not most of the original signs have disappeared. Here is the location and name of each site.
Trade River Valley Trade River begins with a branch - Butternut Creek coming out of Luck and another branch coming from swamps between Luck and Frederic. This traces the river and some of the historic sites, dams etc.
Atlas History Some of the historic sites around Atlas in Laketown Township Polk Co
St Croix River History Some of the people who lived along the St Croix River from St Croix Falls to Grantsburg
1873 Mail Routes for Polk County Mail came from Stillwater to Star Prairie then Osceola and St Croix Falls in November of 1873. This is the route based on a newspaper
1864 Route St Paul MN to Superior WI trail An 1864 issue of Harper's Magazine detailed a trip from St Paul to Superior. This attempts to locate the route. The story is interesting. St Paul to Superior
Google Maps are an interesting and free way to show locations with markers. Behind each marker can be text, photos, links etc. They are easy to make and give a geographical view of history. It would be interesting to do layers in time so, for example, one could see the mail routes as they changed over time.