Born in Chicago, Muir studied at the Art Students League under Richard Lahey and at the University of Maine. Her work was primarily portraiture. Muir moved with her husband William Muir, a sculptor and painter, to Stonington, Maine in 1939. She exhibited at the Maine Art Gallery, the University of Maine, the Salons of America, and has works in the collection of the Farnsworth Art Museum, Rockland, Maine. She was the first woman appointed to the National Commission of Fine Arts, under President Eisenhower, and was also an accomplished architect and conservationist, having donated her property on several Maine islands to the Nature Conservancy for preservation.