One of the critical problems in the delineation of the Omaha Trade Area to be solved by the geographer is the selection of the agricultural hinterland of Omaha. A series of maps, based on the 1959 and 1964 Census of Agriculture reports were developed. These basic maps were correlated with known data concerning agricultural shipments to the Omaha market. The result was the definition of an agricultural core region centered on Omaha.
Retallick, Harold J. and Gildersleeve, Charles R., "Geographic Background Report No. 1: Omaha's Agricultural Core Region" (1967). Publications Archives, 1963-2000. 506.