Central Pennsylvania, May 31, 1889: After a deluge of rain—nearly a foot in less than twenty-four hours—swelled the Little Conemaugh River, panicked engineers watched helplessly as swiftly rising waters threatened to breach the South Fork dam, built to create a private lake for a fishing and hunting club that counted among its members Henry Clay Frick and Andrew Carnegie. Though the engineers telegraphed a warning to neighboring towns, residents—factory workers and their families—remained in their homes, used to false alarms.

At 3:10 p.m., the dam gave way, releasing 20 million tons of water. Traveling 40 miles an hour, with swells as high as 60 feet, the deadly floodwaters razed the mill town—home to 20,000 people—in minutes. The Great Flood today remains the deadliest in U.S. history, killing more than 2,200 people and causing $17 million in damage. In Ruthless Tide, Al Roker follows an unforgettable cast of characters whose fates converged because of that tragic day.