The Johnstown Flood, sometimes referred to locally as the Great Flood of 1889, occurred on Friday, May 31, 1889, after the catastrophic failure of the South Fork Dam, located on the south fork of the Little Conemaugh River, 14 miles (23 km) upstream of the town of Johnstown, Pennsylvania, United States. The dam ruptured after several days of extremely heavy rainfall, releasing 14.55 million cubic meters of water. With a volumetric flow rate that temporarily equaled the average flow rate of the Mississippi River, the flood killed 2,208 people and accounted for US$17 million (equivalent to $551 million in 2025) in damage. By loss of life it was by far the worst flash flood in U.S. history.
The American Red Cross, led by Clara Barton and with 50 volunteers, undertook a major disaster relief effort. Support for victims came from all over the United States and 18 foreign countries. After the flood, survivors suffered a series of legal defeats in their attempts to recover damages from the dam's owners. This led in the 20th century to American Tort law allowing, in some circumstances, strict liability rather than fault-based liability.
The events have been commemorated nationally as well as locally. The Johnstown Flood National Memorial was established in 1964. The National Historic Landmark District of the South Fork Fishing and Hunting Club was established in 1986. Both are administered by the National Park Service.
History
The city of Johnstown, Pennsylvania was founded in 1800 by Swiss immigrant Joseph Johns (anglicized from "Schantz") where the Stonycreek and Little Conemaugh rivers joined to form the Conemaugh River. It began to prosper with the building of the Pennsylvania Main Line Canal in 1836.
Construction of the Pennsylvania Railroad and the Cambria Iron Works in the 1850s brought further industry to town, and eventually led to abandonment of the canal. By 1889, Johnstown's industries had attracted numerous Welsh and German immigrants to work. With a population of 30,000, it was a growing industrial community known for the quality of its steel.
The high, steep hills of the narrow Conemaugh Valley and the Allegheny Mountains to the east restricted development of Johnstown, keeping it close to the riverfront areas. The valley received large amounts of runoff from rain and snowfall. The area surrounding the city is prone to flooding due to its location on the rivers, whose upstream watersheds include an extensive drainage basin of the Allegheny plateau. Adding to these factors, slag from the iron furnaces of the steel mills was dumped along the river to create more land for building and narrowed the riverbed. Developers' artificial narrowing of the riverbed to maximize early industries left the city even more flood-prone.
Immediately downstream of Johnstown, the Conemaugh River is hemmed in by steep mountainsides for about 10 miles (16 km). A roadside plaque alongside Pennsylvania Route 56, which follows this river, proclaims that this stretch of valley is the deepest river gorge in North America east of the Rocky Mountains.
South Fork Dam and Lake Conemaugh
High above the city, the Commonwealth of Pennsylvania built the earthenwork South Fork Dam between 1838 and 1853 as part of a cross-state canal system, the Main Line of Public Works. Johnstown was the eastern terminus of the Western Division Canal, supplied with water by Lake Conemaugh, the reservoir behind the dam.
As railroads superseded canal barge transport, the Commonwealth abandoned the canal and sold it to the Pennsylvania Railroad. The dam and lake were part of the purchase, and the railroad sold them to private interests.
Henry Clay Frick led a group of Pittsburgh speculators, including Benjamin Ruff, to purchase the abandoned reservoir, modify it, and convert it into a private resort lake as a property for their wealthy associates. Many were connected through business and social links to Carnegie Steel.
Development included lowering the dam to make its top wide enough to hold a road for a carriageway and putting a fish screen in the spillway. Workers lowered the dam, which had been 72 feet (22 m) high, by 3 feet (0.91 m). These alterations are thought to have increased the vulnerability of the dam. Moreover, a system of relief pipes and valves, a feature of the original dam which had previously been sold off for scrap, was not replaced. The club had no way of lowering the water level in the lake in case of an emergency.
The Pittsburgh speculators built cottages and a clubhouse to create the South Fork Fishing and Hunting Club, an exclusive and private mountain retreat. Membership grew to include more than fifty wealthy steel, coal, and railroad industrialists.
Lake Conemaugh at the club's site was 450 feet (140 m) in elevation above Johnstown. The lake was about 2 miles (3.2 km) long, about 1 mile (1.6 km) wide, and 60 feet (18 m) deep near the dam. The dam was 69 feet (21 m) high and 931 feet (284 m) long.
Events of the flood
On May 28, 1889, a low-pressure area formed over Nebraska and Kansas. By the time this weather pattern reached western Pennsylvania two days later, it had developed into what would be termed the heaviest rainfall event that had ever been recorded in that part of the United States. The U.S. Army Signal Corps estimated that 6 to 10 inches (150 to 250 mm) of rain fell in 24 hours over the region. During the night of May 30, small creeks became roaring torrents, ripping out trees and debris. Telegraph lines were downed and rail lines were washed away. Before daybreak, the Little Conemaugh River and Stoney Creek, which form the main stem of the Conemaugh River at their confluence in Johnstown, were threatening to overtop their banks.
On the morning of May 31, in a farmhouse on a hill just above the South Fork Dam, Elias Unger, president of the South Fork Fishing and Hunting Club, awoke to the sight of Lake Conemaugh swollen after a night-long heavy rainfall. Unger ran outside in the still-pouring rain to assess the situation and saw that the water was nearly cresting the dam. He quickly assembled a group of men to save the face of the dam by trying to unclog the spillway, where an iron grate and a broken fish trap had become obstructed with debris from the swollen waterline. Other men tried digging a ditch at the other end of the dam, on the western abutment which was lower than the dam crest. The idea was to let more water out of the lake to try to prevent overtopping of the crest in the center, where the dam was structurally weakest, but the effort was unsuccessful. Most men remained on top of the dam, some plowing earth to raise the crest above the water, while others tried to pile mud and rock on the face to save the eroding wall.
John Parke, an engineer for the South Fork Club, briefly considered cutting through the dam's end near the abutments, where the pressure would be less, in order to create another spillway, but eventually decided against it as doing so would have quickly ensured the failure of the dam. Twice, under orders from Unger, Parke rode on horseback to a telegraph office in the nearby town of South Fork to send warnings to Johnstown explaining the dangerous situation unfolding at the dam. Parke did not personally take a warning message to the telegraph tower – he sent a man instead. The warnings ultimately were not passed to the authorities in Johnstown, however, as there had been many false alarms in the past of the dam not holding against flooding, and most people felt the danger was not serious enough to warrant urgent delivery of the messages. Unger, Parke, and the rest of the men continued working until exhaustion to save the face of the dam; they abandoned their efforts at around 1:30 pm, fearing that their efforts were futile and recognizing that the dam was at risk of imminent collapse. Unger ordered all of his men to fall back to high ground on both sides of the dam where they could do nothing but watch and wait. During the day in Johnstown, the situation worsened as water levels rose to as high as 10 feet (3.0 m) in the streets, trapping some people in their houses.
Between 2:50 and 2:55 pm the South Fork Dam breached. Lidar analysis of the Lake Conemaugh basin reveals that it contained 14.55 million cubic meters (3.843 billion gallons) of water at the moment the dam collapsed. Witnesses reported that the lake took only 35–45 minutes to empty completely after the dam began to fail, though modern dam-breach computer modeling reveals that it likely took approximately 65 minutes for most of the lake to empty. The first town to be hit by the flood was South Fork, immediately downstream; the town was on high ground, and most of the people escaped by running up the nearby hills when they saw the dam spill over. Between twenty and thirty houses were destroyed or washed away, and four people were killed.
Continuing on its way downstream to Johnstown, 14 miles (23 km) by river to the west, the water picked up debris such as trees, houses, and animals. At the Conemaugh Viaduct, a 78-foot-high (24 m) railroad bridge, the flood was momentarily stemmed when debris jammed against the stone bridge's arch. But within seven minutes, the viaduct collapsed, allowing the flood to resume its course. Owing to the delay at the stone arch, the flood waters gained renewed hydraulic head, resulting in a stronger, more abrupt wave of water hitting places downstream than otherwise might have been expected. The small town of Mineral Point, one mile (1.6 km) below the viaduct, was the first populated place to be hit with this renewed force. About thirty families lived on the village's single street. After the flood, there were no structures, no topsoil, no subsoil in Mineral Point – only the bedrock was left. The death toll here was approximately sixteen people. In 2009, studies showed that the flood's flow rate through the narrow valley exceeded 420,000 cubic feet per second (12,000 m3/s), comparable to the flow rate of the Mississippi River at its delta, which varies between 250,000 and 710,000 cu ft/s (7,000 and 20,000 m3/s).
The village of East Conemaugh was the next populated area to fall victim to the flood. One witness on high ground near the town described the water as almost obscured by debris, resembling "a huge hill rolling over and over". From his idle locomotive in the town's railyard, engineer John Hess heard and felt the rumbling of the approaching flood. Throwing his locomotive into reverse, he raced backward toward East Conemaugh, the whistle blowing constantly. His warning saved many people who reached high ground. When the flood hit, it picked up the still-moving locomotive off the tracks and floated it aside; Hess himself survived, but at least fifty people died, including about twenty-five passengers stranded on trains in the village.
Just before reaching the main part of Johnstown, the flood surge hit the Cambria Iron Works in the town of Woodvale, sweeping up railroad cars and barbed wire. One survivor from Cambria City described the moment the rush hit: "In 15 minutes the water rose 10 feet, and in five minutes more I am sure 50 houses came floating down the streets. There were people in every one of them, and God only knows how many were lost." He described the houses jamming together and being battered to pieces before carrying far, and recalled that when he looked back from the flood, "where Cambria City stood there was nothing but a great lake of water." Of Woodvale's 1,100 residents, 314 died in the flood. Boilers exploded when the flood hit the Gautier Wire Works, causing black smoke seen by Johnstown residents. Miles of barbed wire became entangled with the rest of the debris in the flood waters.
Fifty-seven minutes after the dam collapsed, the flood reached Johnstown. Residents were caught by surprise as the wall of water and debris bore down, traveling at speeds of 40 miles per hour (64 km/h) and reaching a height of 60 feet (18 m) in places. Some people, realizing the danger, tried to escape by running towards high ground, but most were hit by the surging floodwater in their homes and workplaces. Many people were crushed by pieces of debris, and others became caught in barbed wire from the wire factory upstream. Those who reached attics or roofs, or managed to stay afloat on pieces of floating debris, waited hours for help to arrive.
The Stone Bridge, a substantial arched structure, carried the Pennsylvania Railroad across the Conemaugh River in the center of Johnstown. The debris carried by the flood, now including twisted steel rails, boxcars, entire buildings, and the bodies of the flood's victims, formed a temporary dam at the bridge, forcing the flood surge to roll upstream along the channel of the Stoney Creek River. Eventually, gravity caused the surge to return to the dam, resulting in a second wave that hit the city from a different direction. Some people who had been washed downstream became trapped in an inferno as the debris that had piled up against the bridge caught fire; at least eighty people died there. The fire burned for three days. After floodwaters receded, the pile of debris at the bridge was seen to cover 30 acres (12 ha), and reached 70 feet (21 m) in height. It took workers three months to remove the mass of debris, the delay owing in part to the huge quantity of barbed wire from the ironworks entangled with the wreckage. Dynamite was eventually used.