According to David Walls, The Bureau of Agricultural Economics within the U.S. Department of Agriculture published Economic and Social Problems and Conditions of the Southern Appalachians in 1935 in response to “a cluster of organizations including the Conference of Southern Mountain Workers, the Home Missions Council, the Council of Women for Home Missions, the Federal Council of the Churches of Christ in America, and Community Church Workers.”
“The USDA study contains a section by F.J. Marschner which divides Southern Appalachia into three major divisions” and “16 physiographic subregions,” totaling 236 counties in nine states (what we call the USDA full region). “The rest of the USDA study limits itself to 205 counties in six states” (what we call the USDA small region).
United States Department of Agriculture (USDA). The Bureau of Agricultural Economics Bureau of Home Economics, and Forest Service. 1935. Economic and social problems and conditions of the Southern Appalachians. Washington, DC.
Walls, David. 1977. On the naming of Appalachia. In An Appalachian symposium: Essays written in honor of Cratis D. Williams, edited by J.W. Williamson. Boone, NC: Appalachian State University Press.