In 1946, Dunning became Thayer Lindsley Professor of Applied Science at Columbia. In the immediate post-war years he was Scientific Director for Construction of the Nevis Laboratories, a collaborative effort of Columbia University, the United States Atomic Energy Commission, and the Office of Naval Research. He became Dean of the School of Engineering and Applied Science in 1950. This ended his active research career, but he was active in fundraising for what became the Seeley Wintersmith Mudd Building and the Terrace Engineering Center extension. By the time he stepped down as Dean in 1969, he had raised $50 million for the school.