Burt, William Austin, 1792-1858, Higgins, Sylvester W. (1847). 50N 39W - Survey Map of Rockland Township, Ontonagon County [Michigan]. Department of Natural Resources. https://michigan.access.preservica.com/uncategorized/IO_e1ff7ab1-f2cb-4bc1-a6ed-abc213eb73c2 (map)