Around World War I, homesteaders flocked in mass to the southern Great Plains, where they replaced the native grasses that held the topsoil in place with wheat and other crops. Eschewing sustainable agricultural practices, such as crop rotation, they managed to reap big harvests during the wet years of the 1920s. But when a prolonged drought struck in the 1930s, the now eroded and nutrient-poor soil began blowing up into huge dust clouds that ravaged the landscape. As one “black blizzard” hit after another, harmful dust particles accumulated in people’s lungs, causing hundreds of deaths and sickening thousands. Dead livestock and wildlife littered the ground. By the time the drought ended, up to one-third of the most affected homesteaders had fled the Southern Plains for greener pastures.