Burt, William Austin, 1792-1858, Houghton, Douglass, 1809-1845 (1845). 57N 31W - Survey Map of Sherman Township, Houghton Township, and Eagle Harbor Township, Keweenaw County [Michigan]. Department of Natural Resources. https://michigan.access.preservica.com/uncategorized/IO_a038c1df-300d-4477-a282-e0aadeba3411 (map)