Plot of the Unknown - Grandview Cemetery - Westmont. PA - Graves of the Unknown on Waymarking.com

The Great Flood of 1889
“At around 3:10 p.m., the South Fork Dam burst, allowing the 20 million tons of Lake Conemaugh to cascade down the Little Conemaugh River. It took about 40 minutes for the entire lake to drain of the water. The first town to be hit by the flood was the small town of South Fork. Fortunately, the town was on high ground and most of the people ran farther up the nearby hills when they saw the dam spill over. Despite 20 to 30 houses being destroyed or washed away, only four people were killed.

On its way downstream toward Johnstown, the crest picked up debris, such as trees, houses, and animals. At the Conemaugh Viaduct, a 78-foot (24 m) high railroad bridge, the flood temporarily was stopped when debris jammed against the stone bridge's arch. But after around seven minutes, the viaduct collapsed, allowing the flood to resume its course. Because of this, the force of the surge gained renewed momentum, resulting in a stronger force hitting Johnstown than otherwise would have been expected. The small town of Mineral Point, one mile (1.6 km) below the Conemaugh Viaduct, was hit with this renewed force. About 30 families lived on the village's single street. After the flood, only a bare rock remained. About 16 people were killed.

The village of East Conemaugh was next to be hit by 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". Locomotive engineer John Hess, sitting in his locomotive, heard the rumbling of the approaching flood and, correctly assuming what it was, tried to warn people by tying down the train whistle and racing toward the town by riding backwards to warn the residents ahead of the wave. His warning saved many people who were able to get to high ground. But at least 50 people died, including about 25 passengers stranded on trains in the town. Hess himself miraculously survived despite the flood picking up his locomotive and tossing it aside.

Just before hitting the main part of the city, the flood surge hit the Cambria Iron Works at the town of Woodvale, taking with it railroad cars and barbed wire. 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 the Johnstown residents.

Some 57 minutes after the South Fork Dam collapsed, the flood hit Johnstown. The inhabitants of Johnstown were caught by surprise as the wall of water and debris bore down on the village, traveling at 40 miles per hour (64 km/h) and reaching a height of 60 feet (18 m) in places. Some, realizing the danger, tried to escape by running towards high ground. But most people were hit by the surging floodwater. Many people were crushed by pieces of debris, and others became caught in barbed wire from the wire factory upstream. Those who sought safety in attics, or managed to stay afloat on pieces of floating debris, waited hours for help to arrive.

At Johnstown, the Stone Bridge, which was a substantial arched structure, carried the Pennsylvania Railroad across the Conemaugh River. The debris that was carried by the flood formed a temporary dam, stopping further progress of the water. The flood surge rolled upstream along the Stoney Creek River. Eventually, gravity caused the surge to return to the dam, causing a second wave to hit the city, but from a different direction.Some people who had been washed downstream became trapped in an inferno as debris that had piled up against the Stone Bridge caught fire, killing at least 80 people. The fire at the Stone Bridge burned for three days. Afterwards, the pile of debris there covered 30 acres (12 ha), and reached 70 feet (21 m) in height. The mass of debris took three months to remove, because of the masses of steel wire from the ironworks binding it. Dynamite was eventually used to clear it. The Stone Bridge is still standing, and is often portrayed as one of the images of the flood.

Aftermath
The total death toll was 2,209, making the disaster the largest loss of civilian life in the United States at the time. It was later surpassed by the 1900 Galveston hurricane and the 9/11 attacks (in which, coincidentally, one of the hijacked airliners crashed near Shanksville, just 20 miles (32 km) south of Johnstown). Some historians believe the 1928 Okeechobee hurricane also killed more people in the U.S. than did the Johnstown Flood, but the official death toll was lower.

Ninety-nine entire families died in the Johnstown deluge, including 396 children. One hundred twenty-four women and 198 men were left without their spouses, 98 children lost both parents. Seven hundred seventy-seven victims (1 of every 3 bodies found) were never identified and rest in the Plot of the Unknown in Grandview Cemetery in Westmont. An 'eternal flame' burns at Point Park in Johnstown, at the confluence of the Stonycreek and Little Conemaugh Rivers, in memory of the flood victims."
Source: Wikipedia: Johnstown Flood