Fifty years after the catastrophic rupture of the Tones Dam in eastern Idaho, residents of the Upper Snake to Snake River Valley are reflecting on a disaster that killed 11 people and destroyed much of Rexburg and Sugar City. The June 1976 flood, which sent a wall of water through multiple communities, has left a dual legacy of engineering reform and profound community resilience.
The morning of the collapse, 1976, begins with leaks forming on the dam face as engineers attempted to patch growing wet areas using bulldozers. By 8:30 a.m. on Saturday, June 5, parts of the newly constructed dam appeared like a sieve, according to Church News reporting. As the breach expanded, workers were forced to abandon their machinery because the face of the dam continued to collapse around them. At 11:52 a.m., the dam suffered a catastrophic rupture, creating a 1,000-foot long, wedge-shaped gash that released water at a rate of 2 million cubic feet per second—a volume triple that of Niagara Falls, according to the National Fire Protection Association (NFPA). The reservoir emptied entirely by 8 p.m. that evening, flooding an area of 300 square miles.
The disaster began in the early days of June 1976 when engineers at the Teton Dam noticed wet areas appearing on the face of the massive earthen structure. The dam, which had been completed the previous fall at a cost of approximately $100 million, sat on the Teton River and was designed to provide irrigation, hydropower, and flood control for the Upper Snake River Valley. While site analyses had previously identified minor weak spots, heavy spring runoff caused by an exceptional snowpack rapidly increased the volume of water in the 17-mile-long reservoir.
Path of destruction through Idaho communities
The floodwaters moved with devastating force through the region, reaching heights of 10 to 30 feet in some locations. By 2 p.m., a 15-foot tidal wave struck Sugar City, followed by a similar bombardment of Rexburg at 2:30 p.m. The destruction was widespread; by late afternoon, reports described Rexburg as looking like an army war zone. Local police and neighbors used bullhorns and house-to-house visits to spread evacuation warnings, eventually moving some 35,000 people to higher ground, including many at Ricks College, now BYU–Idaho.
The path of destruction extended roughly 90 miles southward along the Snake and Teton River basins. The water passed through Idaho Falls, where it rose dangerously close to the sandbagged Idaho Falls Idaho Temple, before moving through Blackfoot and finally being halted by the American Falls Dam three days later.
Economic devastation and personal loss
The physical and economic toll was immense, with damage estimates reaching as high as $2 billion. The flood destroyed 32 miles of railroad tracks, seven bridges, and hundreds of miles of roads. In some agricultural areas, the force of the water stripped topsoil down to bare rock, while other sections were left buried under two feet of gravel and rock. Beyond infrastructure, the disaster claimed between 16,000 and 20,000 livestock.
For local residents, the loss was deeply personal. Martell Grover, who owned a jewelry and watchmaking business on Rexburg’s Main Street, recounted losing both his home and his livelihood to the flood. He recalled finding dead cattle in his backyard and between his house and its foundation, noting that the experience served as a reminder of human vulnerability.
Engineering failures and safety reforms
In the wake of the collapse, an investigating panel identified several design and construction flaws as the cause of the failure. These included issues with the soil used in the dam's core and cracks in the rock abutments that allowed water to seep through the earthen structure. In response to these findings, the U.S. Bureau of Reclamation established the Dam Safety Program, which has since become a worldwide standard for dam construction.
Today, very little remains of the original structure; only the spillway and a portion of the dam are still standing, as no attempts have been made to rebuild it.
Community resilience during bicentennial celebrations
Despite the devastation, the community's response during the 1976 bicentennial celebrations became a symbol of local strength. Although the flood occurred just four weeks before planned festivities for America's 200th birthday, residents chose to hold a parade on July 3, 1976, to boost morale. Clyde Anderson, then-chairman of the bicentennial committee, noted that while people had lost nearly everything, they wanted to demonstrate pride in their heritage.
The parade featured hand-painted signs and makeshift floats made from flatbed trucks. A rodeo held in nearby Rigby—necessitated because the Rexburg grounds were destroyed—featured a rider who famously stood back up after being unseated by a bucking bull, an act that residents viewed as a symbol of their own perseverance.
A legacy of faith and rebuilding
Fifty years later, Rexburg City cultural arts director Jed Platt views the disaster's true legacy as the resiliency of the people. In coordinating a commemorative exhibit at Rexburg City Hall, Platt noted that the way members of the local Latter-day Saint community supported one another is a significant part of their history.
For historians and residents alike, the anniversary serves as both a memorial to the 11 lives lost and a celebration of the spirit required to rebuild a community from the mud and debris left behind by the Teton River.
