Minnie Baldwin was born at High Green, Sheffield, on 6 November 1871, the daughter of Thomas Baldwin, schoolmaster, and Elizabeth Hobson. She was the elder sister of Mabel Rosaline Baldwin (Girton 1899). Minnie was educated at Sheffield High School, followed by a year at Bedford College, London. She came to Girton in 1890 as a College Scholar to study Natural Sciences and won the Thérese Montefiore Memorial Prize in 1894. Minnie Baldwin was a lecturer in science at Westfield College, London, from 1894-1897. In 1897 she married John Christopher Willis, then Director of the Peradeniya Botanical Gardens, at Kandy in Ceylon. They had three daughters: Eleanor Beatrice Willis (later Browning, known as Betty); Margaret Swainson Willis (later Anderson - Girton 1921); and Anita Willis. Minnie Willis died in August 1931.