“Not much corn was grown in Kentucky”
Meant to say
“Not much cotton was grown in Kentucky” compared to the Deep South states.
Here is one version of the map showing US economic regions in 1860, this one shows where large numbers of slaves lived, and didn't live.
Important to notice that in regions with few to no slaves, there were hotbeds of Unionism within the Confederacy -- notably, western Virginia, eastern Tennessee, western North Carolina, Northern Alabama and Northern Arkansas.
The map does not show the numbers of slaves in New Mexico (native Americans enslaved) and Oklahoma (owned by Native Americans).