Frémont, John Charles. "Map to illustrate an exploration of the country lying between the Missouri River and the Rocky Mountains, on the line of the Nebraska or Platte River." Map. Washington, D.C: s.n., [1843]. Norman B. Leventhal Map & Education Center, https://collections.leventhalmap.org/search/commonwealth:4m90fb25g (accessed April 19, 2024).