He later served as a Colonel and assembled a militia to help quell the Upper Canada Rebellion, although they were never called to action.
He spent most of his professional life as a Crown agent in the area surrounding Peterborough, Ontario assigning plots of land to settlers, advocating for projects to improve the infrastructure, and settling disputes as a Justice of the Peace.
He was elected to the Legislative Assembly of Upper Canada in 1834 and reelected in 1836 by relying on his reputation after helping settlers and running on a pro-British platform.
[3] During the Upper Canada Rebellion McDonell, by that point promoted to major, commanded the 2nd Regiment Northumberland militia.
[5] To improve the production of various mills and businesses McDonell lobbied the Legislative Assembly of Upper Canada to develop a route along the Trent–Severn Waterway.
[4] He ran for the new Legislative Assembly of the Province of Canada in the Colborne District in 1841 as a conservative but was defeated by John Gilchrist by a large margin.
He disagreed with French-speaking bishops who added democratic principles and ideas to their public school curriculum and he was shocked at the level of discontent and uprising happening in Lower Canada.
[3] He had fallen out of favour with the church and upon his death in Peterborough in 1861 his body was refused a Roman Catholic burial.