Highly detailed map of Dakota Territory, published by OW Gray & Son.
The map is colored by counties and showing towns, roads, railroads, Post Offices, etc.
Many counties not yet formed.
O. W. Gray was a publishing firm based in Philadelphia. Later, they published as O. W. Gray & Son. They published atlases in the late nineteenth century. Gray's National Atlas was one of the most successful commercial ventures of the 1870s and one of the last to employ hand coloring on maps.