The collection consists largely of typescript and photostatic copies of the Walkers' diaries and papers, although the original of Elkanah Walker's 1842 diary is included, along with a few original letters.

The collection includes Elkanah Walker's diaries for 1838, 1841, and 1842, and Mary Richardson Walker's diaries for 1838, 1847, and 1852. Diary entries from 1838 to 1847 describe the Walkers' overland journey with fellow missionaries William H. Gray, Cushing Eells, and Myra F. Eells, including hardships along the trail, child bearing and nursing, and arguments among the missionaries; and missionary work both at the Whitman mission at Waiilatpu and the Walkers' own mission at Tshimakain. Mary Richardson Walker's 1852 diary describes life in Forest Grove, Oregon.

The collection also includes correspondence of Elkanah Walker (1837-1868) and Mary Richardson Walker (1828-1885) concerning religious and personal matters, mission operations, the Whitman killings, and the Cayuse War. Correspondents include Henry Harmon Spalding, Marcus Whitman, Narcissa Prentiss Whitman, William Henry Gray, David Greene, Cushing Eells, Peter Skene Ogden, John Lee Lewes, and Mary Richardson Walker's parents, Joseph Richardson and Charlotte Richardson. Some letters contain anti-Catholic and anti-Indigenous sentiments.

Additional materials in the collection include: an 1865 letter from one of Elkanah Walker and Mary Richardson Walker's sons, Cyrus H. Walker, to another of the Walkers' sons, brother Samuel T. Walker, about military service at Fort Hoskins; and Samuel T. Walker's handwritten transcript of an 1853 letter sent to Elkanah Walker, with Samuel T. Walker's own commentary.