Mary Elizabeth Tennant was born in New Castle, Colorado on October 4, 1894. After obtaining her B.A. from the University of Colorado in 1916, she went on to attend the Vassar Rainbow Division Training Camp for nurses during the summer of 1918. She received her nursing education at Philadelphia General Hospital and Simmons College, later earning a Masters of Public Health from Johns Hopkins University in 1949.
Tennant's 27-year tenure at the Rockefeller Foundation began in 1928 as Field Director of the Division of Medical Education in Europe. Later, she served as a member of the International Health Division (IHD) staff, specializing in nursing and public health, and she eventually rose to become Assistant Director in 1945. During her time with the IHD, she was able to travel extensively, both in Europe (where she was stationed for many years) and around the globe.
Ten years after her retirement from the Foundation, in 1965, Tennant received an honorary doctorate from her alma mater, the University of Colorado. She died in 1986.