The Denver and Middle Park Railroad Company was incorporated under the general laws of the State of Colorado, and a certificate of incorporation was issued by the Colorado Secretary of State on April 17, 1883. The enterprise proposed to build and operate a railroad from Denver via Ralston Creek to Hot Springs, Grand County, Colorado. A survey was completed within a year for a railroad over Berthoud Pass. In 1884 the Union Pacific acquired control of the Denver and Middle Park and altered its construction plans. Subsequently, a 4.56 mile narrow gauge line was built from Ralston, on the Colorado Central Railway (which the Union Pacific also owned) to stone quarries at Glencoe. The line was operated in conjunction with the Colorado Central until April 1, 1890, when, with other companies, The Denver and Middle Park Railroad became part of the Union Pacific, Denver & Gulf Railway Company.

The collection contains minutes (1883-1890); stock subscription book (1883-1890); trial balances (1886 – 1890); stock ledger (1889-1890); journal (1885-1890); and ledger (1885-1890).