Mary Heister Reid was born in Reading, Pennsylvania. She studied at the School of Design in Philadelphia. George A. Reid was one of her Anatomy instructors where they became friends and started sketching together. They married in 1885. Returning from their honeymoon trip to Europe they came back to Toronto. They gave classes in painting and had joint exhibitions of their paintings. As time went on she got more and more recognition for her still-life paintings, garden flowers and intimate interior scenes.