The majority of the material in this record group was in labelled folders or envelopes; while these headings were preserved, a series order was imposed during processing.

The first series contains background material on the railroad and includes correspondence, newspaper clippings, illustrative items such as time tables, and annual reports, journal articles, maps of Northern Pacific lands (the parent company of the Camas Prairie), track laying records and a souvenir of a 1960 passenger excursion from Lewiston to Grangeville.

The second series contains a large number of photographs of trains, engines, and bridges. These are arranged alphabetically by the collector. Some collectors have only their own photographs, while others added photographs of other collectors to their own collections. For this reason there is a small amount of duplication in the folders. Some folders also contain correspondence concerning the identification of photographs. Many of the photographs are copies. Photographs used in the book are identified on the verso with the chapter and photograph number within the chapter, e.g. 2-12 is chapter 2, the 12th photograph.

The final series contains permits allowing Riegger on railroad property, track profiles, and tapes of oral history interviews with retired Camas Prairie employees; transcripts of these tapes are also included.