DATE: July 1951
LOCATION: Kansas and Missouri
ESTIMATED COST: $21 billion*
WHAT HAPPENED: Intense rainfall from the Great Plains caused Kansas River flooding that overtopped levees in two states, inundating both state capitals and Kansas City. About 2 million acres were flooded, 45,000 homes damaged or destroyed, and bridges and locomotives washed away.
*All costs estimated in 2009 dollars.