These records are divided into two subgroups: Rocky Fork and Cooke City Railway Company; and Green and Keefe.

The RF & CC records are arranged in seven series:

The incoming correspondence (1888-1889) consists of telegrams to A.J. Merritt, chief engineer for RF & CC, concerning the purchase and transfer of supplies, the progress of construction and problems encountered, the hiring of workers, etc.; and other correspondence, primarily to A.J. Merritt, concerning construction of the line and financial arrangements.

The outgoing correspondence consists of three letterpress volumes (1888-1889). One volume is the correspondence of John Buskett, secretary of the Rocky Fork Town and Electric Company, primarily to Samuel T. Hauser, president of the Rocky Fork Town and Electric Company, concerning the finances of the RF & CC. The volume also contains correspondence from A.J. Merritt concerning financial matters of the RF & CC. In addition, the volume contains financial statements concerning the construction of the RF & CC. The two other volumes are primarily correspondence of A.J. Merritt written from Billings to RF & CC and NP officials in Laurel and St. Paul, Minnesota, and Samuel Hauser about the construction of the RF & CC, the progress of construction, etc. Also included are lists of material used in construction and financial statements listing construction costs.

The financial records (1888-1890) include a breakdown of construction expenditures by type of material or service purchased; payrolls; a folder of miscellaneous papers including invoices, bills for board, and financial statements; and two volumes of miscellaneous records including vouchers, financial statements, payrolls, and estimates for work performed by subcontractors.

The legal documents (1888-1890) include contracts with construction contractors, a contract between Samuel Hauser and the RF & CC, etc.

The maps (1889) are preliminary surveys of the country through which the RF & CC lines were to pass, and a map showing the lines route through the Crow Reservation.

The reports (1887-1889) are prose surveys of potential railroad routes and construction progress reports.

The miscellany (1885-1889, undated) consists of lists of material used in construction, lists of materials supplied the RF & CC by the NP, a record of waybills received at Laurel, Montana by the NP, a sketch of proposed arrangement of tracks and buildings at Laurel, track profiles, and linens and blueprints of primarily NP railroad structures such as bridges, engine houses, switches, etc. Also included are blueprints and linens of the RF & CC and the Union Pacific, and a list of materials required for Northern Pacific, La Moure, and Missouri Railroad culverts and bridges.

The records of Green and Keefe are arranged in four series:

The general correspondence (1889-1890) concerns the construction of the Boulder-Elkhorn line including the purchase of supplies, progress of construction, the hiring of workers, etc.

The outgoing correspondence (1889-1890) consists of two letterpress volumes concerning financial matters, of which one volume primarily deals with the construction of the Boulder-Elkhorn line.

The financial records (1889-1890) are subcontractors' estimates of value of work performed, bills served Green and Keefe by the NP for services rendered and car rentals, payrolls, trial balances, and a cost book listing food and general merchandise purchased by Green and Keefe.

The legal materials consist of a contract between the NP and Green and Keefe for work on the Boulder-Elkhorn line.

One map of Yellowstone National Park has been transferred to the Library Map Collection.