The largest part of the collection consists of the pocket diaries Parkhurst kept from 1847 to 1906. The early diaries (1847-1860) relate details of his court cases and only rarely mention his personal life. Records of various financial transactions are incorporated in these early diaries. The diaries of the war years (1861-1865) include battle accounts and descriptions of Parkhurst's experiences as a prisoner-of-war in 1862. In the diaries of the post-war years, Parkhurst discusses primarily his business affairs and political problems. The diaries of 1888 and 1889 are of particular interest since they cover his tenure as Minister of Belgium.

Parkhurst's correspondence mainly consists of letters written to his sisters during the war and exchanges with various government officials relating to his appointments to governmental positions.

Most of the speeches included in the collection were delivered at regimental reunions. Two are clearly political in scope: one was used in Parkhurst's own campaign and one for Horace Greeley's Presidential campaign.

The newspaper clippings largely relate to reunions but a few give biographical sketches of Parkhurst. Several also deal with political affairs of the post-war era.

The collection also includes microfilm copies of materials from this collection, and the John Gibson Parkhurst papers at the University of Michigan Bentley Historical Library.