1912 – Born on June 5th in in Milwaukee, Wisconsin. He is the Curator of Birds for the American Museum of Natural History.
1937 – Joined the Museum after graduating from Hobart College.
1940 – Dean was appointed Assistant Curator.
1947 – He received his doctorate at Cornell University with a thesis on Hawaiian honeycreepers.
1950 – Appointed as Associate Curator.
1955 – He was appointed as Lamont Curator.
1957-1973 – He was Chairman of the Department.
2003 – Passed away at his home in Tenafly, New Jersey at age 90.