Best known for her publications about Canada's medical history, Margaret Ridley Charlton also co-authored stories and poems for children.

After the early death of her father, Captain John Charlton (b. c1815), Margaret Anne Charlton assumed the middle name Ridley to honour her father's descent from the Anglican martyr Bishop Nicholas Ridley (c1500-1555). Similarly, she fashioned her pseudonym, "Lynn Hetherington," from the name of the family's ancestral mansion in Northern England. Born in Lower Canada and educated at home until she was sixteen, in 1874 she became one of the first female students admitted to the High School of Montreal. After graduation, and before working as a Montreal schoolteacher in the early 1880s, she joined the editorial staff of the , to which she contributed historical sketches. She collaborated with her friend Charlotte Fraser to produce children's stories and historical romances, among them (1892), purportedly the first book of fairytales published in Canada. was followed two years later by another collaboration between the two authors, (1894).

After the publication of this second collection, Margaret redirected her career to librarianship, a profession not yet established in Canada and thus requiring that she attend a summer course at Amherst College in Massachusetts. Her first position was as librarian at the YMCA library. In 1895, she joined the staff at the Medical Faculty Library at McGill University, breaking into the predominantly male arena of academic librarianship; in 1896, she was appointed Assistant Librarian there, a post she held for eighteen years.

Having studied under Melvil Dewey (1851-1931) at Amherst College, Margaret was greatly involved in the development of library systems and librarianship as a discipline. She was one of the founders and indeed by some accounts the instigator of the Association of Medical Librarians (now the Medical Library Association) in 1898; another of the eight founding members, Marcia Noyes, noted that "Miss Charlton was the one person who indirectly brought the Association into being."

Margaret was a forceful personality and clashed at times with her male colleagues; her superior, Dr. Finley, wrote in 1936, though, that her "vagaries … were more than balanced by her energies and ability." Dr. Finley, however, retired in 1913, and in 1914, "after a year of intolerable friction," Margaret moved to Toronto, where she assumed the post of Librarian at the Academy of Medicine. She remained in this position until her retirement in 1922.

Late in life, Margaret resumed her literary and historical writing, contributing to academic journals. Her major work, published in the (1923-24), established the foundation for later scholarship. After retirement, she returned to live with her sisters in Montreal, where she died in 1931. In 2003, she was designated a "Person of National Historical Significance" by the Government of Canada for her work as a librarian and co-founder of the Medical Library Association.