This collection contains the 1866 diary of John C. Anderson which documents his journey from St. Louis, Missouri to Virginia City, Montana and back. Anderson's diary documents his travels and experiences while crossing the plains into the Rocky Mountains and contains detailed information about early Eagle Rock (modern day Idaho Falls, Idaho). His diary is both descriptive and reflective, and also contains numerous illustrations. In addition to Anderson's 1866 diary, this collection contains a second transcribed and edited version of his original 1866 diary. Although Anderson's reasons for creating the second diary are not stated, it is believed that Anderson created the edited version in hopes of selling it to a publisher. However, the second diary was never published.

Anderson's 1866 diary was transcribed and published in 1973 by Glen Barrett. See; Barrett, Glen, Mackinaws Down the Missouri, Utah State University Press, Logan, Utah, 1973. See USU SC&A's call # 917.8 An23.