Did the north or south have flat rivers?

Platte

The Platte over most of its length is a broad, shallow, meandering stream with a sandy bottom and many islands—a braided stream.

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Platte River.

Platte River Nebraska River, Shallow River, Ñíbraxge (iow), Pȟaŋkéska Wakpá (lkt), Ní Btháska (oma), Kíckatus (paw)

so they can differentiate themselves from others as they saw themselves as the superior race. the star was basically a symbol that meant you are a less of a person than i am because of my race. the star was also degrading for those who had to wear it because they were aware of this and the nazis used the notion to make them feel less like a person.