west of the Mississippi River. That operation was performed at the Salt Lake General Hospital (SLGH, now University of Utah Hospital) on an adult with an atrial septal defect. Nelson was also the director of the University of Utah thoracic surgery residency program. In March 1956, he performed the first successful pediatric cardiac operation at the SLGH, a total repair of tetralogy of Fallot in a four-year-old girl. He was at the forefront of surgeons focusing attention on coronary artery disease, and contributed to the advance of valvular surgery as well. In 1960, he performed one of the first-ever repairs of tricuspid valve regurgitation. His patient was a Latter-day Saint stake patriarch. He also provided the first surgical intervention for tricuspid regurgitation, a disorder that allows blood to flow backward into the right upper heart chamber. In an indication of his surgical skill, a 1968 case series of his aortic valve replacements demonstrated an exceptionally low peri-operative mortality. Later, he performed the same operation on future LDS Church president Spencer W. Kimball, replacing his damaged aortic valve. In 1985, Nelson along with his colleague, Conrad B. Jenson, performed a quadruple bypass surgery on the Chinese opera performer (1925–1989). Nelson first operated out of the University of Utah's medical school. He later had a practice at the Salt Lake Clinic with admission privileges at LDS Hospital. In 1964, he set up his own private practice with him as the lead and Conrad Jenson as an associate. In 1966, Nelson became head of the thoracic residency program that combined resources from the University of Utah Medical School, LDS Hospital, Primary Children's Hospital and the VA Hospital in Salt Lake City. In 1965, the University of Chicago offered Nelson the position as head of their department of thoracic surgery. Dallin H. Oaks, then a law professor at Chicago and a fellow Latter-day Saint, actively worked to recruit Nelson. However, after consulting with David O. McKay, Nelson turned down the offer. Nelson became involved with the administrative aspects of medicine and was elected president of the Utah State Medical Association. He was chair of the Division of Thoracic Surgery at LDS Hospital. In 1981, Nelson held appointments as a visiting professor of surgery at the National Institute of Cardiology in Mexico City and the Catholic University in Santiago, Chile. In May 1982 he was a visiting professor at the Hospital de Clinicas in Montevideo,