Science now reveals the true cause of the dam breach flood that destroyed Johnstown in 1889. The tragic loss of more than 2200 lives was preventable; the initial investigation of the flood was hijacked, delayed, and distorted by powerful members of the industrial elite. This book bridges the gap between history and science, reexamining eyewitness accounts of the flood and historic documents about the investigation, and applying new LiDAR, GPS, and hydraulic studies to solve the mystery - what caused the Great Flood of 1889? The book includes a notable chapter on the "sister" of the South Fork Dam, "The Forgotten Dam" at Hollidaysburg, PA.