Mitchell, S. Augustus, Jr. (Samuel Augustus). North western America : showing the territory ceded by Russia to the United States ; reduced from the map published by the U.S.C.S. Dept., map, 1870; (https://texashistory.unt.edu/ark:/67531/metapth298514/m1/1/: accessed December 9, 2018), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .