Born and raised in North Prairie, Wisconsin, with her four sisters, Mary Beth Larsen attended Mukwonago High School from 1988 through 1992. In high school, she ran and lettered in the track and field program all four years, and was co-captain her senior year. Cross country season is one of her favorite memories from high school and competed three fall seasons on the varsity squad. Twice qualifying for the state meet, she was named rookie of the year her freshman season and received the spirit award her junior year. As a senior, Mary Beth opted to compete on the newly formed co-operative swim team at Waukesha North. A competitive swimmer since the age of nine, she was excited to compete in the state meet.
Mary Beth maintained a high GPA all four years, graduating near the top of her class. She also participated in many extra-curricular activities, including 4-H, youth group at Waukesha Bible Church, and the local Pony Club. After graduation, she moved to attend New Mexico Military Institute in Roswell, New Mexico, where she began training in the Modern Pentathlon, a multi-sport event consisting of shooting, fencing, swimming, equestrian stadium jumping, and running. Mary Beth graduated with an Associate of Arts degree as the class salutatorian and moved on to full-time training for the 1996 Olympic Games. The women, however, were not included on the program and she resumed her college education at Marquette University.
Chiropractic college was next and she entered Logan College of Chiropractic in August 1996. She qualified and competed in the 1998 Hawaii Ironman World Championships where she finished third in her age group. Her Olympic dream called and she took a leave of absence from school in order to train for pentathlon again. She won the gold medal at the 1999 Pan American Games, becoming the first woman to qualify for the 2000 Olympic Games in Sydney, Australia. Mary Beth finished fourth place, just short of the bronze medal and soon thereafter, she went back to receive her Doctor of Chiropractic degree in December of 2001. Chiropractic practice would wait as she returned to full-time training for the 2004 Athens Olympic Games. In the summer of 2004, she competed in her second Olympic Games, finishing fifteenth overall.
During her athletic career, Mary Beth was featured in multiple magazine and newspaper publications, including ESPN The Magazine, Sports Illustrated, and Brilliant magazine. She was featured on the cover of Esquire magazine as one of the sexiest athletes in the nation in August 2000. Experience Life magazine featured Mary Beth on the cover of their May 2005 edition.
Not long after the Olympics, she moved back to the Midwest, landing in Anoka, Minnesota to practice chiropractic full-time. Her parents still live in North prairie, Wisconsin and Mary Beth visits often. She is not married and has two dogs, Sasha and Diego. Recently, Mary Beth accepted a position with Standard Process, a whole food supplement company (Palmyra, WI), and will be returning to live in southeastern Wisconsin