United States. Post Office Dept. "Post route map of the states of Montana, Idaho and Wyoming with adjacent parts of N. & S. Dakota, Nebraska, Colorado, Utah, Nevada, Oregon, and Washington showing post offices with intermediate distances and mail routes in operation on the 1st of October 1891." Map. Washington, D.C.: Post Office Dept., 1891. Norman B. Leventhal Map & Education Center, https://collections.leventhalmap.org/search/commonwealth:cj82kj897 (accessed April 25, 2024).