Margaret Ritchie was born in Bay City, Michigan, June 5, 1895, the daughter of John W. and Helen (White) Ritchie. She spent her early life there, graduating from Eastern High School in 1914. She received a diploma from Skidmore School in Saratoga Springs, New York in 1916, then attended Columbia University Teachers College in New York City where she received her B.S. degree in 1918 and her M.A. in 1930.

She was an assistant instructor of foods and chemistry at Columbia before joining the home economics staff at Battle Creek College in Michigan where she taught for 18 years, eventually becoming director of the home economics department. When the school closed its doors in 1938 Ritchie came to the University of Idaho as head of Home Economics. She retired as department head in 1959, but continued to teach until forced to retire because of age in 1965. She then taught at California Polytechnic College in Pomona until 1968 when she returned to Moscow to live.

She was active in university, community, and professional affairs during her 47 years in Moscow. She was a member and officer in many organizations including the Home Economics Association, Idaho Home Economics Association, American Diatetics Association, and Moscow Dieticians Group. She served on the board of Church Women United and was active in Meals on Wheels and the Moscow Chamber of Commerce. She was also a member of the American Association of University Women and the PEO Sisterhood.

Margaret Ritchie died in Moscow on January 7, 1986, at the age of 90. Her body was cremated and the ashes sent to Bay City for burial.