Blueprints, circa 1898-circa 1913, collected by Theodore Dengler, an alumnus of the Michigan Mining School in Houghton, Michigan. Dengler worked at the Atlantic, Baltic, Mohawk and Wolverine mines. Includes blueprints of machinery, buildings, and maps, mainly from the Atlantic and Baltic mines with some from the Mohawk, Wolverine, Allouez, Champion and Central mines. Also includes correspondence and other printed ephemera.