The collection consists of papers of and relating to missionaries Marcus and Narcissa Whitman. A substantial portion of the collection consists of letters that they wrote to Narcissa Whitman's family. These letters describe the Whitmans' overland journey to the Pacific Northwest in 1836, and their lives as missionaries in the following decade. The letters also frequently express frustration with Native peoples' cultural norms and their reluctance to convert to Calvinist Christianity, often using patronizing and derogatory language. The letters also include pejorative terms for Roman Catholics and for biracial people of Native and European or Euro-American descent.

Other writings by the Whitmans include typescript copies of their correspondence with the American Board of Commissioners for Foreign Missions, and a typescript of Marcus Whitman's proposed legislation to establish outposts to assist Euro-American emigrants traveling westward. Other materials in the collection include original and reproduced materials regarding the Whitman killings and their aftermath; microfilm of Mary Saunders and Helen Saunders' recollections of the Whitman killings and aftermath; and items related to the memorialization of the Whitmans, including efforts in the 1890s to erect a monument in their honor.