Corn Production Moving North?

Stealing from this site: Schnitkey, G. "Changes in Where Corn Is Grown in the Last Ten Years." farmdoc daily (6):135, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign, July 19, 2016. Permalink: http://farmdocdaily.illinois.edu/2016/07/changes-in-where-corn-is-grown-last-ten-years.html It seems corn production is moving northward.  Can't imagine the reason why.