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.

[7] 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 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.

High above the city, the Commonwealth of Pennsylvania built the South Fork Dam between 1838 and 1853 as part of a cross-state canal system, the Main Line of Public Works.

[9] 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 at a property for their wealthy associates.

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.

The Pittsburgh speculators built cottages and a clubhouse to create the South Fork Fishing and Hunting Club, an exclusive and private mountain retreat.

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 U.S.

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.

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.

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.

[12] 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,[9] and most people felt the danger was not serious enough to warrant urgent delivery of the messages.

During the day in Johnstown, the situation worsened as water levels rose to as high as 10 feet (3.0 m)[13] in the streets, trapping some people in their houses.

[14] 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.

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.

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.

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.

[17] The total death toll from the flood was calculated originally as 2,209 people,[1] making the disaster the largest loss of civilian life in the U.S. at the time.

However, as pointed out by historian David McCullough,[2] a man reported as presumed dead had survived; Leroy Temple returned to Johnstown eleven years after the disaster and revealed he had extricated himself from the flood debris at the Stone Bridge, walked out of the valley, and moved to Beverly, Massachusetts.

[19] At ASCE's annual convention in June 1890, committee member Max Becker was quoted as saying, "We will hardly [publish our investigation] report this session, unless pressed to do so, as we do not want to become involved in any litigation.

[3] A hydraulic analysis published in 2016 confirmed that the changes made to the dam by the South Fork Fishing and Hunting Club severely reduced its ability to withstand major storms.

In the years following the disaster, some survivors blamed the members of the South Fork Fishing and Hunting Club for their modifications to the dam that lowered its level and gradually blocked a spillway.

This perceived injustice is considered to have aided the acceptance, in later cases, of a new definition of "strict, joint, and several liability," so that even a "non-negligent defendant could be held liable for damage caused by the unnatural use of land.

[24] Popular feeling ran high, as is reflected in Isaac G. Reed's poem: Many thousand human lives- Butchered husbands, slaughtered wives Mangled daughters, bleeding sons, Hosts of martyred little ones, (Worse than Herod's awful crime) Sent to heaven before their time; Lovers burnt and sweethearts drowned, Darlings lost but never found!

[1] Working seven days and nights, workmen built a wooden trestle bridge to temporarily replace the Conemaugh Viaduct, which had been destroyed by the flood.

$3,742,818.78 was collected for the Johnstown relief effort from within the U.S. and 18 foreign countries, including Russia, France, Germany, Great Britain, Australia, and the Ottoman Empire.

At Point Park in Johnstown, at the confluence of the Stonycreek and Little Conemaugh rivers, an eternal flame burns in memory of the flood victims.

Supporters of the memorial also believed it was important to gain control over the remaining buildings and property of the former South Fork Fishing and Hunting Club, in order to have full interpretation.