Detailed map of the state of Minnesota, colored by townships and showing counties, towns, rivers, canals, etc.
An excellent large format map of the period from one of the major American map publishers of the 1870s.
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.