Atlas of Historical County Boundaries: Old Northwest Historical Boundary Data File [ACB]
To compile a machine-readable data file of all changes in the international, territorial, state, county and Congressional district boundaries, plus locations of governmental seats and pertinent names of the states of the Northwest (Ill., Ind., Mich., Ohio, Wis.) between 1788 and 1970. The data file format provides a product more economical, flexible and versatile than printed maps and atlases. Researchers will be able to make various uses of the file from overlays for modern maps to bases for historical maps and atlases.