Their official name was the Sisters of Charity of Montreal. It was founded by Marie-Margueritte Dufrost de Lajemmerais, the widow of bootlegger Francois Youville. She and her three assistants in helping the poor made a secret pact to devote themselves completely to their task. About ten years later they took over running the Hopital General of Montreal from the Charon Brothers. Locals were not pleased with the changeover, and started calling them "les souers grises", or grey sisters, as a derogatory term. They were also called by some "the tipsy sisters" as a reference to Margueritte being the widow of a bootlegger. When they were recognized as an official religious order in 1755, they took the name "Grey Nuns" as their official name. Along with the name, they kept their simple grey habits, as a tribute to their humble origins.
In the beginning, the Grey Nuns filled a much needed role in New France. Women in difficulty were not taken care of outside of family. The hospital only treated men. The Grey Nuns filled this void. Not only treating women, though, their mandate was to feed and house any poor person, In exchange, able bodied people were put to work helping to run the day to day of the building. People could do laundry, prepare meals, sew; whatever way they could help.
In 1755, the nuns devoted themselves to caring for the sick during the smallpox epidemic. Since they were not a cloistered order, they were able to help the Oka First nations people at this time as well. In gratitude, they were among the contributors to rebuild after a devastating fire to the order in 1765.
Margueritte died 23 December 1771. The nuns continued with her legacy. In the 1840's the nuns expanded. They took over running a hospital in St-Hyacinthe, Quebec, and an orphanage in Quebec City. A chapter opened in St, Boniface, Manitoba on the Red River, and they opened a school in Ottawa. In 1855, they started in the U.S. by beginning work in Toledo, Ohio during a cholera epidemic. During the 1920's-1940's, they opened several locations across the Prairie Provinces. In the 50's- 70's they expanded their work to South America and Africa.
In 1959, Margueritte has made a saint by Pope Saint John XXIII. She was the first Canadian born saint.
You can find out more about the Grey Nuns and their work here: