BroJoeK, I can’t tell whether those percentages are 1.0-2.0% or 10-20%.
My late father was from She(lby) County, near the top right. It is purple on your map. That horizontal band across the state is interesting. It must reflect some geographical feature.
Certainly the larger, beginning at less than 10% (green) and growing to over 30% (red).
"That horizontal band across the state is interesting. It must reflect some geographical feature."
Yes, as colorado tanker mentioned above: "The darker region north of the Missouri River was known as Little Dixie and had some smaller scale plantation agriculture."
That's the Missouri river you see.