Kansas Joe McCoy and Memphis Minnie first wrote and recorded When The Levee Breaks in '29. The lyrics reflect experiences during the upheaval caused by the Great Mississippi Flood of 1927, the most destructive river flood in the history of the United States, with 27,000 square miles (70,000 km2) inundated in depths of up to 30 feet (9 m) over the course of several months in early 1927.
Nice slide show for this tune.