Is it a systematic surveying error or something else that made these county borders this way? I’d assume a surveying error because they occur latitudinally rather than longitudinally, and latitude is harder to figure:
Nebraska (see Sioux, Dawes, Box Butte, Sheridan, Cherry, Brown, Rock, and Holt counties)
Kansas (Hamilton, Kearny, Finney, Gray, Ford, Edwards)
Iowa (Woodbury-Grundy, Harrison-Jasper)
In Iowa’s case it looks like maybe they were trying to keep some uniformity of area going given how Woodbury is carved out by the Missouri, but then see Harrison.
Surely there’re other ways of ensuring equal size (though it’s not clear that’s what they were going for, given the counties’ other dimensions) besides repeating an error through several counties. When you get the Eastern border wrong, why not just say to Hell with it, rather than repeating it through the next several counties?