Burt, William Austin, 1792-1858, Houghton, Douglass, 1809-1845 (1845). 56N 31W - Survey Map of Sherman Township, Keweenaw County [Michigan]. Department of Natural Resources. https://michigan.access.preservica.com/uncategorized/IO_7471a634-3484-44cc-9586-78d4c1e76458 (map)