Starting in 1930 the Minnesota Historical Society picked the sites and wrote the inscriptions for a run of roadside historical markers, and the State Highway Department made the signs and set them up. By 1940 there were 112 of them on the state's trunk and U.S. highways, and a WPA survey published a guide that printed all 112 inscriptions word for word. 107 of them are on the map. Each page has the whole 1940 entry and the old maps that cover that spot.
The First Iron Mine marker near Soudan records that the first commercial shipment of Minnesota iron ore left the Breitung pit on July 31, 1884, over a railroad Charlemagne Tower and associates had just finished building to open the Vermillion Range. Under the pin is a Map of Northern Minnesota from 1874, ten years earlier. It letters Vermillion Lake right where the pin sits. Around it the mapmaker drew forest in every direction and one road running south.
Marker text comes from the 1940 guide, "Guide to Historic Markers Erected by the State Highway Department Cooperating with the Minnesota Historical Society," published by the Minnesota Historical Records Survey Project, Work Projects Administration. It is public domain and credited on every page.
https://treealive.com/markers/mn
Five of the 112 could not be placed from what the book says. One of them, entry 99, gives a location that lands in one county and names another, so there is no pin I can defend. Nothing in the guide is a coordinate, so the pins are my best reading and the pages say so. These pages show the 1940 book, not what stands on the road now. The text is served exactly as printed, including the era's own terms, and every page carries a line saying Minnesota now calls the 1862 conflict the U.S.-Dakota War and has since replaced the wording on some of these signs.
The site's actual job is family trees. I ran my own Pennsylvania family through it and it turned up 77 markers near the places they lived. Free, no account needed.
Source: r/minnesota · by /u/Total-Ad4827