May I hazard a WAG? Iowa and northern Missouri have tons of old-ethnic German-Americans who, during the Civil War, were solidly pro-Lincoln.
The reason for this -- and I think it still operates today -- is that Germans have a strong cultural orientation toward authoritarianism that didn't fall into the ocean when they immigrated. Even Texas Germans were Unionists in 1860-1861, and very prickly about it -- some of them were lynched for their outspokenness and possible involvement in Lincoln's underground Wide Awakes (who were accused of plotting slave rebellions and arson campaigns).