The main difference between Iowa and Missouri is that the former was largely settled by Yankees from New England who brought with them a more liberal political culture than the Southerners who settled the latter.
More so along the Mississippi. When my mother was growing up in Davenport, Iowa, in the 1920's and 1930's, the cultural and class differences between the WASPS and Germans was palpable, including considerable neighborhood segregation.
IIRC before WWI a lot of Germans over there still spoke German as mother tongue. They were persecuted after WWI and their German schools got banned.
