Mitchell, S. Augustus (Samuel Augustus), 1792-1868. Map of the chief part of the western states and part of Virginia. Engraved to illustrate Mitchell's School and Family Geography., map, 1839; (https://texashistory.unt.edu/ark:/67531/metapth251934/m1/1/: accessed October 16, 2018), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .