Mignon Redfield Waterman was born October 13, 1944 in Billings, Montana to Zell Redfield of Michigan and Mable Young Redfield of Nebraska. Both Zell and Mable grew up on homesteads north of Roundup. The land on which Zell's homestead stood remained in the family until 1965; sadly, Mable's family lost their homestead during the Depression. During his adult life, Zell worked as a ranch hand, cowboy, and truck driver, ultimately operating an auto repair shop. Mable worked as a cook, house cleaner, and eventually for the Billings Post Office. After retiring, Mable moved to Boulder, where she served on the City Council.

Mignon Redfield Waterman graduated from Billings High School in 1963, continuing her education at the University of Montana where she majored in Journalism. She married Ronald F. Waterman, and the two had two sons, Briar and Kyle. Mrs. Waterman had a long and varied career in public service, beginning with her time on the Helena Civic Center Board (1977-1984), four years of were served as Treasurer and Fund Drive Chair. Between 1982 and 2013, she served on myriad other boards, including the Helena Industries Board of Directors, St. Peter's Hospital Foundation Board of Directors, the Helena YMCA Board of Directors, the Kay McKenna Youth Foundation Board of Directors, and, most recently, the Helena Civic Television Board of Directors and the Grandstreet Theatre Board of Directors.

Between 1986 and 1990, Mrs. Waterman worked as a lobbyist for the Montana Association of Churches. In 1990, she was elected the Senator for Senate Distinct 26, a position she held until 2002. During her tenure as Senator, Mrs. Waterman also worked as the Public Relations Coordinator for the Montana Council of Teachers of Mathematics Systemic Initiative for Montana Mathematics and Science project (1991-1996). As a Senator, Mignon served on numerous committees, including the Senate Finance and Claims Committee, Children's Mental Health System of Care Committee, and the Senate Education Committee.