Where this source supports the record
Each entry separates the article’s editorial relevance note from its exact, section-level claims. A bibliography link without a direct claim is labeled plainly.
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Engineering failures · 31 May 1889Open article references →
The Johnstown Flood
South Fork Dam ruins and Conemaugh Valley flood path · United States
Why editors use it hereTechnical and chronological history of construction, alterations, overtopping, failure, travel time, and losses.
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Quick read
On 31 May 1889, the South Fork Dam failed after intense rain and released about twenty million tons of water into Pennsylvania's Conemaugh Valley.
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Trigger and conditions
A major storm saturated the watershed overnight.
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Uncertainty
The official 2,209 count was carefully compiled but omitted some unidentified and transient victims; the National Park Service notes the actual number may have been higher.
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Why it matters
The rain was natural; the scale of loss was engineered through a dam whose safety margin had been reduced and whose downstream communities had little control over its operation.
Reviewed 26 July 2026
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Quick read