This Is America’s Deadliest Flash Flood on Record

As summer turns to fall, the rainy season begins and dumps water across the continental United States. Sometimes, severe weather patterns erupt that drop excessive levels of rain on an area within a short period. Sometimes, these weather patterns drop so much rain so quickly that it leads to a phenomenon called flash floods. Usually, flash floods occur when excessive water collapses at a natural or man-made stoppage point like a dam. While flash floods happen every year, usually to mild effects, one incident remains the worst flash flood in US history.

Flash floods kill more people than any other weather phenomena including hurricanes, tornadoes, and lightning. The worst flash flood to ever occur in the United States is called The Great Flood of 1889. It occurred after a nearby dam overflowed and unleashed a torrent of water down a nearby river into the town of Johnstown, Pennsylvania. In this article, we will further explore the conditions that led to the worst flash flood in US history, the timeline of events, its aftermath, and the fallout of the disaster that had wide-ranging effects on American law. (For other scorched earth storms, discover wildly destructive storms that flattened entire cities.)

To compile an article about the worst flash flood in US history, 24/7 Tempo consulted a range of historical, heritage, and news publications including the Johnstown Area Heritage Association, The Geo-Institute, and The Zebra. Next, we selected information that provided a clear and accurate picture of the conditions that caused the worst flash flood in history. After that, we confirmed aspects of the information using sites like the Library of Congress Research Guides and The National Weather Service.

Swiss immigrant Joseph Johns founded the city of Johnstown, Pennsylvania in 1800 where the Stoneycreek and Little Conemaugh Rivers merged into the Conemaugh River. After construction on the Pennsylvania Main Line Canal began in the 1830s, Johnstown began to prosper. A decade or so later, the town abandoned the Main Line Canal. This happened after the establishment of the Pennsylvania Railroad and the Cambria Iron Works. These industries attracted many German and Welsh immigrants, boosting the population to over 30,000.

From the outset, geographical limitations restricted the expansion of Johnstown. The precipitous hills of the Conemaugh Valley and the nearby Allegheny Mountains kept the city cloistered on riverfront areas. Even before the founding of Johnstown, the valley was prone to flooding. After the erection of nearby steel mills, industry dumped slag from its iron furnaces along the river to both narrow the riverbed and provide more space for buildings.

Even today, a sign sits on Pennsylvania Route 56 downstream of Johnstown proclaiming this portion of the valley to be the deepest river gorge east of the Rocky Mountains. The conditions were set for the worst flash flood in history, but it first required a catalyst.

Between 1838 and 1853, the Commonwealth of Pennsylvania built the South Fork Dam high above the city to further its state canal system. With the advancement of railroad technology, the Commonwealth deserted the Main Line Canal and adjoining dam. Soon after, a group of speculators led by Henry Clay Frick bought the abandoned reservoir, looking to convert it into a private lake for wealthy figures connected to the Carnegie Steel Company.

Upon purchase, the speculators built cottages and a clubhouse as part of the new South Fork Fishing and Hunting Club. Simultaneously, workers lowered the dam from 72 feet to 69 feet high. Furthermore, the new owners also sold off the dam's system of pressure valves and relief pipes for scrap metal. Soon, membership for the club swelled to include numerous steal, coal, and medal industrialists.

The conditions were in place. The refurbishment of the South Fork Dam set the stage for the worst flash flood in history. All it required to kick off was an anomalous level of weather activity that could overflow the already weakened damn. That dark fortune manifested in the early summer of 1889. (For weather's creation instead of destruction, discover 50 stunning natural wonders formed by weather.)

On May 28, 1889, a low-pressure weather area formed over the Midwest. Two days later, the weather pattern migrated over western Pennsylvania and metastasized into the heaviest rainfall event ever recorded in that region of the United States. According to estimates by the United States Army Signal Corps, 6 to 10 inches of rain fell in 24 hours. As a result, babbling creeks transformed into rushing rivers, taking out trees and telegraph lines. Before the sun rose the next day, the stems of the Conemaugh River already threatened to overflow.

Early on May 31st, the South Fork Fishing and Hunting Club president Elias Unger awoke to find water already cresting the top edge of the dam. Immediately he assembled a group of men to unclog the spillway or find some relief for the gushing water before it toppled the dam at its structurally weakest point. Soon, engineer John Parke joined the crew. Unger ordered him to ride to the nearby telegraph office and send a warning to authorities in Johnstown. Though he reached the telegraph office, his warnings were never sent. Fear of dam overflow was a routine concern in the area, and workers at the telegraph office felt this new development did not warrant a message.

Parke returned to the emergency crew, who worked until the early afternoon attempting to save the dam's face. Their efforts, however, proved futile and they abandoned their attempt. Unger ordered the men to nearby high ground where they watched and waited. Thanks to the unheard-of rain activity, water in the river began rising in Johnstown.

According to the best estimates, the South Fork Dam breached between 2:50 and 2:55 pm. Within an hour, 14.55 million cubic meters of water emptied from the dam and rushed down the hillsides. The town of South Fork, downstream from the dam, took the first hit. However, most of its residents escaped harm after running to high ground upon seeing the dam collapse.

Merging with the Connemaugh River, the flash flood continued downstream toward Johnstown 14 miles away. As it gained speed and size, it picked up the debris of trees, buildings, and animals. For a brief moment, the Conemaugh Viaduct stopped the flooding water. Within minutes, however, the force crushed this railroad bridge/viaduct and continued toward Johnstown with increased vigor. Residents of Johnstown looked up in terror to find a 40-mile-an-hour wall of water rushing at them, reaching a height of 60 feet in some places.

While people attempted to run up the hills, the flood crushed many. By now, the flood carried box cars, mangled railroad tracks, the bodies of victims, and even entire buildings. After gravity surged the water back toward the dam, Johnstown was hit with another flood from the opposite direction. Debris that piled up against the Conemaugh bridge eventually caught fire, trapping dozens of people in a massive fire that burned for three days.

Once the waters of the worst flash flood in history receded, it revealed an untold path of destruction. Piles of debris from the destruction covered over 30 acres and in some places, reached 70 feet in height. The flood wiped the city of Johnstown off the face of the earth. The original death toll was calculated at 2,209 people, with bodies from the accident being found as far away as Cincinnati, Ohio. Some of them were not found for another two decades. In total, 99 entire families perished in the flood, including 396 children. Furthermore, 1/3 of the victims, some 777 people, were never identified. Barring proper identification, these mysterious remains were interred at the nearby Grandview Cemetery.

Quickly, it became apparent that this flood was the worst flash flood in US history. Over 1,600 homes were destroyed, and the flood caused $17 million in property damage (equivalent to $550 million today). Little was left of Johnstown, as the flood completely vaporized four square miles of its downtown. While the Cambria Iron and Steel's facilities met heavy damage, they returned to operation in as little as 18 months.

Clara Barton, the founder and president of the American Red Cross, arrived on the scene before anyone. She stayed for over five months. During that time, donations for the relief effort began pouring in, eventually reaching $3,742,818.78. These donations came from as far away as Russia, Germany, and the Ottoman Empire. Not long after, relief workers arrived and worked day and night to build a wooden trestle bridge, replacing the destroyed Conemaugh viaduct. Demolition expert "Dynamite Bill" Flinn arrived with a 900-man crew to help clear the wreckage and distribute food. At the peak of the cleanup effort, relief workers totaled over 7,000.

A little less than a week after the worst flash flood in US history, the American Society of Civil Engineers (ASCE) created a committee to investigate the cause of the disaster. Several appointed engineers visited the site, reviewed the dam's original blueprint, collected eyewitness reports, and performed hydrologic tests. The ASCE completed its investigative report by January of the following year. However, it took until June 1891 for it to be publicized.

In the final published report, the ASCE concluded that the dam would have failed sooner or later, even if its original design specifications were kept intact. It took another century for experts to dispute these findings. According to a hydraulic analysis published in 2016, changes made to the area by the South Fork Fishing and Hunting Club critically reduced the dam's ability to weather severe storms. Particularly grievous was the dam's height reduction by three feet and the removal of discharge pipes at its base.

For years, many survivors placed the blame on the South Fork Fishing and Hunting Club. Owing to the wealthy standing of the club members, however, the townsfolk saw little recourse for the extreme death and destruction. Furthermore, the law firm Knox and Reed (whose partners were both club members) successfully defended the club in court from culpability, arguing the worst flash flood in US history was an act of god. As such, neither the club nor any of its members were held legally responsible, and no legal compensation was paid to the survivors.

While the survivors of the worst flash flood in US history received no legal compensation for the disaster, some wealthy individual members of the South Fork Fishing and Hunting Club helped out. Co-founder Henry Clay Frick, along with about half of the club's other millionaires, donated thousands of dollars to the relief effort. Furthermore, legendary industrialist Andrew Carnegie built Johnstown a new library.

Today, Johnstown still stands with many monuments commemorating the historic disaster. An eternal flame burns in memory of the flood's victims at the merging of the Stoneycreek and Little Conemaugh rivers. The library built by Andrew Carnegie later transformed into the Johnstown Flood Museum. Furthermore, parts of the stone bridge caught up in the flood have been added to the Johnstown Flood National Memorial.

While this provided some solace for residents, it wasn't enough. Many still hoped to subsume the remnants of the South Fork Fishing and Hunting Club. They got their wish in 1986 when the Federal government designated the club's buildings and surrounding area as a National Historic Landmark District and added to the National Register of Historic Places.

As previously mentioned, the residents of Johnstown found little recourse for the destruction of their town. They functioned as paupers compared to the multimillionaire roster of the South Fork Fishing and Hunting Club. By separating their personal assets from the club's financial structure, it proved difficult to legally find any individual member culpable for the disaster.

The initial court case ruled in favor of the club, citing the flood as an act of god. Recourse would slowly seep in, however, drip by drip. Due to the heavily criticized initial ruling, state courts around the United States adopted a British common law precedent in the 1890s. Called Rylands vs. Fletcher, this precedent held that a non-negligent defendant could be held culpable for damage caused by "unnatural" land use. Though previously ignored, this new law precedent heralded changes. It foreshadowed the American legal system's adoption of strict liability in the 20th century.

All in all, the Johnstown Flood remains the worst flash flood in US history. It grew to such heights thanks to unique geographic formations and careless redesigns of an already unstable reservoir and adjoining dam. As such, it caused apocalyptic levels of destruction and death. Furthermore, thanks to the inequality between the town's working-class residents and the nearby club's inordinately wealthy members, it serves as a potent symbol of the role of economics in any American disaster.

Another one of the worst flash floods in US history was the Heppner Flood of 1903 in Heppner, Oregon. It occurred on June 14, 1903, after a previous storm prevented an incoming storm from seeping into the ground. Instead, it overflowed nearby creeks and rushed into the town of Heppner. While many people made it to higher ground in time, just as many weren't so lucky. The Heppner Flood of 1903 killed 247 people, destroyed 140 total structures, and wiped away 1/3 of the town. The flood caused an estimated $20.3 million in damages (adjusted for today's inflation).

The third worst flash flood in the continental United States happened in South Dakota. Also known as the Rapid City Flood, the Black Hills Flood of 1972 occurred when Rapid Creek overflowed. The flooded creeks pushed past their banks and drained into the nearby Canyon Lake dam. The amount of water proved too much for the dam to bear. It quickly overflowed, breaching its levees with heavy amounts of debris. Soon after, it rushed into the Rapid City, South Dakota. It killed 238 people and destroyed 1,335 homes and 5,000 automobiles. In total, the Rapid City Flood caused $1.17 billion in damages (adjusted for today's inflation rate).

A few years later, another one of the worst flash floods in US history occurred in Colorado. On July 31, 1976, during the state's centennial celebration, a flash flood devastated Big Thompson Canyon. Due to an unexpected thunderstorm in nearby mountains, a torrent of water fell into the canyon causing a flash flood. It killed 143 people, destroyed 400 cars, and eviscerated 470 buildings. It caused millions of dollars in damage. (For other biblical-level weather patterns, explore 15 of the most destructive storms in US history.)