The collection includes papers and correspondence relating to William H. Gray becoming a missionary, the overland journeys he took as a missionary, and his missionary work; a journal from Gray's 1837 overland journey to the East; materials relating to Gray's history of Oregon; and papers related to a land claim dispute with Josiah L. Parrish. Correspondents include fellow missionary Elkanah Walker and American Board of Commissioners for Foreign Missions secretary David Greene.

The manuscript journal of William Gray contains a record of his eastward journey in 1837 from Fort Vancouver to Utica, New York, to recruit additional missionaries for Henry H. Spalding's mission. In the journal, Gray describes his party's interactions with Indigenous peoples along the way, including an altercation with a band of Lakota (Sioux) on August 7, 1837 that, per his account, resulted in the deaths of several of his Indigenous guides and the loss of many of the party's horses and supplies. Also included is a typescript copy (1840-1842) of diary kept by Mary Augusta Dix Gray during her service at various missions, containing infrequent entries describing daily activities and life as a lay missionary.