In Johnstown, Pa., a flood of memories preserved following 1889 disaster More than a century after the devastating flood that took more than 2,000 lives in a matter of hours, the people in Johnstown, Pa., preserve the memories of that fateful day, and the lessons learned about safety and liability that changed American law for future generations. 7:00 am, Apr. 21, 2021 × The stunning visual of uprooted trees and survivors clinging to debris greets visitors upon entering the Johnstown Flood National Memorial in western Pennsylvania. Jim Cheney / Visit Johnstown JOHNSTOWN, Pa. -- Floods -- even the most destructive and relentless ones -- come on slowly and recede slowly in the Red River Valley. The devastation that struck greater Grand Forks in 1997 happened over the course of many days, a few inches at a time, as the communities in its path were gradually engulfed by the cold and muddy waters.