Production of corn and hogs is becoming more concentrated in the four heart-of-the-Corn-Belt states - Iowa, Illinois, Indiana and Ohio - and these same states are holding their own in cattle production, too.
Shepherd, Geoffrey and Ullrich, Kurt
"Our Corn-Hog-Cattle Belt,"
Iowa Farm Science: Vol. 14
, Article 3.
Available at: http://lib.dr.iastate.edu/farmscience/vol14/iss8/3