Grace Johnstone Osborne was born April 21, 1905, in Emerado, North Dakota. She graduated from Emerado High School and entered the University of North Dakota UND) in 1923. Competing in the hurdles, sprints, and running broad jump for the University track team, Osborne became one of the top women athletes in the history of UND. At a 1924 meet, she won the 50 and 100 yard dashes, the 60 yard hurdles, and the broad jump. She finished second in the standing high jump, and placed third in the basketball throw. The results of the meet were telegraphed and compared to results for competitors from across the country. When the results were tabulated, Osborne was declared the national champion. The Dakota Student called her performance "brilliant," while the Grand Forks Herald dubbed her the "Emerado Flash." Besides track and field, Osborne also participated in riflery, basketball, volleyball, and softball.

Since UND did not offer a degree in physical education, Osborne transferred to Mayville Teachers College, earning a teacher's certificate in 1925. For the next ten years, she taught at schools in North Dakota, Montana, and Wyoming. Taking courses in the summer, she graduated with a Bachelor of Arts degree from UND in 1937. Following graduation, she was hired to teach in Devils Lake.

She married Ernest "Hie" Rhonemus in 1941, and returned to UND in 1944 to serve as the Director of Physical Education for Women. She earned a Master of Science degree in Education from UND in 1947. Her thesis was entitled Physical Education in North Dakota High Schools. From 1956 until her retirement in 1975, she was an Associate Professor of Physical Education.

Her work in physical education was not limited to UND. During the 1960s, Rhonemus was well known for her summer physical education workshops for elementary school teachers. The workshops were conducted in Kansas, Oregon, Montana, Utah, and the Dakotas. She also produced several sound recordings designed for use in the physical education of elementary students. The sound recordings became a major part of her workshops.

She was an active member of the American Alliance for Health, Physical Education, and Recreation, the American Association of University Women, and Delta Psi Kappa, an honorary organization for women in physical education. Following her retirement, Rhonemus was active with the Senior Citizens Center and the Humane Society.

Grace Osborne Rhonemus became the first women inducted into the UND Athletic Hall of Fame in 1981. In honor of her athletic achievements, the Grace O. Rhonemus Award is given annually to the UND female athlete of the year. She died April 10, 2002, in Grand Forks.