That religion map bears a rough resemblance to the 1976 map - Methodism and Lutheranism in the Democratic areas, Republicans winning the Catholic areas and the Dutch Reformed northwest corner. (Unlike other Catholic immigrants, German Catholics have historically tended Republican, particularly in the Midwest)
however, the current political geography of Iowa is quite different, with more of an East/West and urban/rural divide
Except Dubuque County, which has always been pretty Catholic. JFK got over 60% in there in 1960, one of only 6 Iowa counties that he won.
