Major Margaret Clothilde MacDonald was born on February 15, 1873, in Bailey's Brook, Nova Scotia.

She was a Canadian military nurse born into a wealthy Catholic family. She attended Mount Saint Vincent Academy in Halifax and Charity Hospital Training School in New York, where she studied nursing. After her graduation in 1895, MacDonald went to Panama to assist as a nurse during the construction of the Panama Canal. She served as a military nurse aboard the military ship Relief during the Spanish-American War in 1898. She also served as a nurse during the South African War in 1900, where she was one of the first females to receive a military commission. After her return to Canada, she was named the Head of the Nursing Service of the Canadian Army Medical Corps. MacDonald moved to Britain to learn from their military nursing program, focusing more on leadership and working to make a change for women. She was the first woman to receive the title of Matron in Chief in the British Empire for her leadership during World War I. In 1920, after many years of nursing, MacDonald retired, returning to her hometown of Bailey's Brook, Nova Scotia, where she died on September 7, 1948.