 He was made collector of customs for the district of Vermont in 1813 and in 1816 President James Madison named Van Ness one of the federal commissioners who negotiated with commissioners from Great Britain to settle the northeastern boundary between the United States and Canada.Initially a member of the Democratic-Republican Party and later a Democrat, he was elected to the Vermont House of Representatives in 1818.He served as Chief Justice of the Supreme Court of Vermont from 1821 to 1823.