[2][3] Established in 1964[4] through legislation signed by President Lyndon B. Johnson,[5][6] it pays tribute to the thousands of victims of the Johnstown Flood, who were injured or killed on May 31, 1889 when the South Fork Dam ruptured.

Established in the center of a narrow floodplain between Little Conemaugh and Stony Creek rivers, the community was surrounded, during the latter part of the nineteenth century, by land that had been altered by deforestation and the leveling of hills.

Ultimately it was purchased by the South Fork Fishing and Hunting Club, an exclusive recreational group composed of wealthy individuals from the Pittsburgh region, for use as a summer mountain retreat.

The club paid for repairs to the dam and additional development: a main building and "cottages" to transform the area into a boating and fishing resort community.

[14][15] On May 31, 1889, the South Fork dam broke from the weight of combined heavy rains and a sudden freshet that had caused a significantly higher amount of water to accumulate in its reservoir than normal.

[18] Property, industry, homes, farms, and lives were destroyed as the water, debris, oil, and bodies of flood victims were caught in the arches of a Pennsylvania Railroad-owned stone bridge.

[13][19][20][21] Although the flood lasted for only ten minutes, the catastrophic damage it caused required five years of cleanup and rebuilding to enable residents of Johnstown to recover.

[22] In addition to the thousands of initial injuries and lives lost, the community was affected by an outbreak of typhoid fever, which developed from bacteria-tainted flood waters and lack of sanitation.

Also conserved by this legislation were the former Lake Conemaugh bed, along with the nearby farm of Elias Unger and the clubhouse of the South Fork Fishing and Hunting Club, which had owned the dam and reservoir.

The visitor center at this national memorial offers two floors of exhibits with maps, views of the former dam, tactile displays, historic photographs of the South Fork Fishing and Hunting Club, a reproduction morgue book, the oral history of flood survivor Victor Heiser, and the film, "Black Friday."