William P. MacKinnon, an American independent historian. A management consultant, MacKinnon is a historian of the American West, Mormon history, and Utah history who was described by Richard E. Turley in 2018 as "the acknowledged expert" and by Thomas G. Alexander in 2019 as "the most knowledgable authority" on what was known in its time as the American War of the Mormons' Succession (or more recently "the Utah War"), a topic of which MacKinnon began his study as a Yale sophomore history major in 1958. In 2018, MacKinnon presented the 35th Juanita Brooks Lecture at Dixie State University: "Across the Desert in 1858: Thomas L. Kane’s Mediating Mission and the Mormon Women who Made it Possible." As of 2010, MacKinnon lived in Santa Barbara with his wife, Patricia.