‘Helped win the Cold War’: Former Nevada Test Site controller dies at 89

A former Nevada Test Site official who for a time was one of three test controllers — people responsible for ensuring the safe execution of nuclear testing — died last week at 89.

John D. Stewart died in St. George, Utah, from pneumonia on Dec. 23, his daughter Vicki Clarke said in a phone interview Tuesday.

Darwin Morgan, a retired spokesperson for the site, said only the U.S. president and the secretary of energy could supersede a test controller.

“Every American that served out there helped win the Cold War, and John was in a very unique position being the test controller for underground nuclear tests,” Morgan said.

Nick Aquilina, who worked at the test site for decades and was in charge of it for seven years, said Stewart was one of his favorite test site employees.

“He was a very quiet man,” Aquilina said. “I never saw him have any kind of temper at all.”

Aquilina said he thinks Stewart was the controller for the last test at the site, now known as the Nevada National Security Site, in 1992.

Morgan said Stewart would have had a role in the final test but was not the controller for it.

Stewart was born Feb. 12, 1935, in Loa, Utah. He grew up on what his daughter described as a “hardscrabble, rattlesnake-infested farm” in Aurora, Utah. His father died when he was 16, and Stewart and his older brother struggled to keep the farm going, but a teacher encouraged them to go to college. Stewart went to Utah State University on a scholarship, Clarke said, worked in a soil sciences lab and earned a soil sciences degree. He got a job at General Electric, then studied as a graduate student at UCLA.

Clarke said her dad wouldn’t say how many nuclear bomb tests he played a role in executing as a civilian employee, but he emphasized the scientific importance of the tests.

“He never wanted any credit for anything” and never spoke negatively of anyone, she said. “He treated people with so much respect and he was so humble that people did their best for him.”

After he retired in 1994, Stewart and his wife served a 14-year Church of Jesus Christ of Latter-day Saints mission at the St. George Bishop’s Storehouse and Cannery, where he was in charge of the technical aspects of the plant’s machinery, according to Clarke and his obituary.

Besides his daughter, he’s survived by Carol Stewart, his wife of 71 years; three other children; 19 grandchildren and 43 great-grandchildren, his obituary said.

Paul Mudra, who worked with Stewart at the test site and was also a test controller, said the position was “very important.”

Testing “basically drove the Russians into defeat because it was a very costly endeavor to do those tests,” he said.

The work in which Stewart took part “deterred (an) adversarial government from forcing a political system on others using a threat of nuclear devastation,” Mudra added. “In other words, it stopped war.”

Contact Noble Brigham at nbrigham@reviewjournal.com. Follow @BrighamNoble on X.