Original at Brigham Young University. Contains diaries "No. 1" (August 1, 1878- May 1879) and "No. 2" (July 20, 1879- December 31, 1879). "No. 1" is largely devoted to church matters, organization of various branches of the Board of Trade, YMMIA, work of Thatcher as Stake President. After April 1879 when Thatcher is ordained to the apostolate, diary is full of central church concerns. Much on the death of his father. "No. 2" deals with the opening of his Mexican Mission. First pages record blessings on him and (p. 73) a "revelation" to his first wife regarding plural marriage.