If you are trying to purchase At the Rim of the Horizon from Amazon.com, I have just been informed that the book will be unavailable there until August 18.
The book is locally available at the South Dakota Agricultural Heritage Museum by phone: 605-688-6226 or by using their email contact form: http://www.sdstate.edu/agmuseum/emailus.cfm. and South Dakota Art Museum. The South Dakota Art Museum may have a limited supply of copies as well: http://www.sdstate.edu/southdakotaartmuseum/shop/index.cfm.
Thank you for your patience!