Focused on Adair County, Missouri, including Kirksville and surrounding areas, this collection encompasses a wide variety of materials from businesses, churches, and organizations. It includes correspondence, newspaper clippings, photographs, maps, and more.

This collection includes P. O. Selby's personal papers, research notes and writings and includes the files and records he gave during his lifetime as well as those found in his campus office after his death. The majority are concerned with Kirksville and Adair County history, genealogies of Adair County families, and Mark Twain.