"The American pioneer peasants were not seizing made-land but virgin soil. Faced with a choice between park-land, forest and steppe, they naturally swarmed toward the latter, for it offered few natural obstacles to the , and seemed to have been made for just such a contingency as the sudden arrival of men far advanced in agricultural techniques. But land which, in semi-arid conditions and in a state of nature, offers few natural obstacles to the plough, is land which will not long stand ploughing; and ought not to be ploughed. The case of Oklahoma... [is] an example of men, considered as a disease of soil, reaching a mortal stage of virulence within half a century."