M. Beatrice Johnstone was born in Glencoe, Minnesota in 1870. Her family moved to Grand Forks in 1883, where she entered Grand Forks High School. She graduated in 1887 and next enrolled at the University of North Dakota. She graduated from UND in 1891, a member of its second graduating class. She was a teacher in Hillsboro, Thompson, and Buxton, North Dakota, from 1891 until 1899. In 1899, she returned to Grand Forks as principal of Washington Grade School. In 1912, she was promoted to superintendent of Grand Forks County Schools.

Johnstone began a long career at the UND in 1925. She was director of the Correspondence Division until 1932, after which she became director of the Extension Division. She served in this capacity until 1955, when she retired. In 1951, she was awarded an honorary Doctor of Humanities degree from UND, as well as being honored with the UND Alumni Distinguished Achievement Citation. In 1952, Johnstone Hall was named in her honor. M. Beatrice Johnstone died September 17, 1959.