He graduated from Princeton University in 1952 with a Bachelor of Science degree in Geological Engineering and at the same time was commissioned a Second Lieutenant in the United States Army Reserves. He then served on active duty for twenty-one months, including a year in Korea in the artillery, where he was awarded the Bronze Star for meritorious service and promoted to First Lieutenant. He received his law degree from Columbia Law School in 1957 and was admitted to the Bar of the State of New York in 1958.
After graduating from Columbia, Mr. Sidamon-Eristoff was associated with the law firm of Kelley Drye Newhall Maginnes & Warren, specializing in commercial banking, corporate and tax law. In 1964, he opened his own law office for the general practice of law. He founded the firm of Sidamon-Eristoff, Morrison, Warren & Ecker in 1978, and was Counsel to the firm of Morrison & de Roos from 1984 to 1988, practicing environmental, land use and administrative law.
From 1989 to 1993 he served as Regional Administrator for Region II of the United States Environmental Protection Agency under Administrator William K. Reilly during the administration of President George H. W. Bush. Mr. Sidamon-Eristoff is Chairman of New York Deep-Water Port Corporation and of NYPort Terminal Development Company LLC.
He is Chairman of the Board of Audubon New York and a Board Member of The National Audubon Society. He is also a Member of the Orange County, New York Planning Board appointed by the County Executive and confirmed by the County Legislature. He was appointed a member of the Advisory Committee for the Hudson River Institute by Governor Pataki. He is Chairman of The Council on Transportation of New York and a Director of the Tri-State Transportation Campaign. He is Secretary and a Director of the New York League of Conservation Voters Education Fund, Inc.
Mr. Sidamon-Eristoff is married to the former Anne Phipps. They have three children: Simon; Elizabeth and Andrew, and eight grandchildren.