Corrill was elected by the primarily Mormon residents of Caldwell County to be the county's first representative to the Missouri State Legislature in August 1838. During this same election, distrust between Missourians and Mormons erupted into an armed conflict, known today as the Missouri Mormon War. Corrill witnessed many key events and was involved in surrendering and turning over Joseph Smith to the state militia, which Smith saw as a betrayal. At the Richmond hearings in November, Corrill testified for the state against Smith and the Mormon actions in the conflict.