McDonell was one of Wayne County's representatives on the Michigan Territorial Council from 1828 through 1835, and served as its president of the council in 1834. He was a delegate to the convention charged with drafting a state constitution in advance of Michigan's application for statehood, and also to the first Convention of Assent called to determine whether Michigan would accept the terms proposed by Congress for Michigan's statehood—taking the western part of the Upper Peninsula in exchange for a strip of land that had been the subject of the Toledo War with Ohio. After the convention rejected the proposal, people requested that Governor Stevens T. Mason call a second convention to reconsider; he refused, but declared that the people themselves could call for such a convention. McDonell was one of several Wayne County residents who signed a statement calling for such a convention, which eventually approved the proposal and removed the last obstacle to Michigan's statehood.
