Here she organized and directed OT and Industrial Therapy programs and instructed student nurses in OT from the University of Michigan, Ann Arbor. From 1939 to 1943 she re-organized OT and set up new programs for patients in specialized environments at Milwaukee Sanitarium in Wauwatosa, Wisconsin. It was during this time that she began to gather material on weaving in order to assist a colleague who wanted to help a patient learn to weave. She also found time to join a number of occupational therapy groups and to produce several professional articles on Occupational Therapy and handcrafts. "By 1940 Black wanted to come home to Nova Scotia. Word of the movement to revive Nova Scotia's rural arts and crafts had reached her in Milwaukee, and she started to write letters to anyone in the province who might advance her interests." In 1942, she was asked by the Province of Nova Scotia to return to the province to organize a provincial handcrafts program. "On August 18, 1942, Harold Connolly, the Minister of Industry and Publicity and a tourism zealot, wrote to Mary Black, an expatriate Nova Scotian and authority on handicrafts: "It is important that we get our arts and crafts set-up into operation immediately and for that reason it is imperative that we secure the services of a director at once." In 1943 she became Supervisor of Handcrafts for the Department of Industry and Publicity (later Trade and Industry), a position she held until her retirement in 1954. Under her guidance, crafts people in rural communities were encouraged to develop and market their work, and classes in crafts were held all over the province to assist fledgling artists. She organized centres to teach and promote weaving, ceramics and needlework. As a result, a more tourism-oriented crafts industry emerged in the province. "Mary Black did not try to direct the efforts of craftspeople. Instead she acted as an enabler, helping producers to improve their work and to find markets for it". During her tenure in the Handcrafts Division, Black provided valuable sponsorship for the development of the Nova Scotia tartan by Bessie Murray in 1953. She retired in 1954, but her 12 years' work in Nova Scotia had a lasting impact. Craftspeople found pride and profit in their work; cottage industries arose which continue to thrive and still provide finely crafted goods. Realizing a need for instructional texts, Mary Black extended her teaching of weaving through writing. Her best known work ‘’The Key to Weaving" began as a series of notes used for occupational therapy purposes.