Clarine Coffin was born and raised in Bangor, Maine, one of six children of Millard Fillmore Coffin and Clara B. Kelley Coffin. She attended the University of Maine at Orono (where she was a member of Phi Beta Kappa and the Class Poet for 1932) and the Hartford Theological Seminary. 

It was while attending seminary that Clarine met the love of her life, Jack Grenfell. Jack was from St. Just, Cornwall, and had immigrated to the US as a child in 1912, along with his two brothers and their parents, the Rev. Thomas and Ethel (Rowe) Grenfell. Clarine and Jack had three children (including the Rev. Dr. John M. Grenfell) and ten grandchildren (including Bard of Cornwall Dr. Trelawney Grenfell-Muir, the Rev. Dr. Tallessyn Z. Grenfell-Lee, and the Rev. Dr. Miranda K. Hassett).

Clarine began teaching at the age of 17 in Hermon, Maine, and later taught at many other schools in Maine and Connecticut, including Hall High School in West Hartford, CT, at which she chaired the English Department. She was a local United Methodist pastor and also worked as an editor and consultant for Reader’s Digest and for the state of Connecticut. 

Clarine established the Grenfell Poetry Prize to recognize outstanding student poets at the University of Maine and was one of the founders of the Maine Fellowship of Christian Writers. In 2002 at the age of 91, Clarine was awarded a Doctorate in Humane Letters by the University of Maine.