Chapter 11 , titled “Fit, Fitting, and Most Fit,” positions McHarg’s approach to environmental design as the continuation of a well-established exploration of the land and life that posed critical questions about the nature of design and the perfectibility of society. The chapter begins with a description of this intellectual family tree beginning with its geologic genesis in the highlands of Scotland with James Hutton, its scientific and cultural development with Charles Lyell, its transformation into a biological thesis of speciation with Charles Darwin, its development into a system of education and cultural criticism with Thomas Huxley, its evolution into a tectonic of environmental reciprocity with Patrick Geddes, its transformation into a modernist design theory with Lewis Mumford, and its redeployment and mobilization into a system of infrastructure with Benton MacKaye. The second part of the chapter examines the correspondence between this natural and cultural history and the landscape master plan that McHarg completed for Washington, D.C. The discussion of the project highlights the role of selection, adaptation, and evolution in the discourse of mid-20th-century environmental design and its problematic, and eugenically tainted relationship to the concept of fitness.