Marilyn earned a Bachelor of Arts degree from St Olaf Collège and a Juris Doctorate degree from the University Denver College of Law. She is a retired partner of the Denver law firm, previously know as Holme Roberts & Owen, where her area of expertise was environmental and natural resource law. She has served on the Board of the Yellowstone Association, the Mesa Verde Foundation and the Western National Parks Association — all friends groups supporting the national parks. As chair of the Yellowstone Association board, she headed a 13 million dollar capital campaign to fund infrastructure needs of the Association. As chair of the Mesa Verde Foundation she launched numerous fundraising efforts to support projects in the Park.