In 1956, Mitchell graduated from Dartmouth College with a BA in the History of Art.
Mitchell received his degree in architecture from Harvard Graduate School of Design in 1962.
Mitchell moved to Barnard, Vermont and continued to practice architecture.
From 2007 until his resignation in 2011, Mitchell served in the Vermont House of Representatives and was a Democrat.
In 2011, Mitchell resigned from the Vermont General Assembly because of lung cancer.