Jerry Rasmussen speculated about the meaning or origin of "Blue Earth" Minnesota. I'm originally from Minnesota (Rochester), and was told that "Blue Earth" is simple description of local soil (or maybe rock). Pipestone, Minnesota, incidentally, was what you might call "international holy ground" for the Indians, because it was here that was located the quarry for the soft, carvable red rock used to make what we palefaces call "peace pipes", more accurately termed "calumets". This stone is easily carvable as it comes out of the ground, and hardens thereafter, I suppose from exposure to air. This holy area was distinguished by the peace with which people from many different tribes, even blood enemies, maintained when meeting there, and by intertribal understanding of peaceable access, even through hostile territory.
And then there's Sleepy Eye, Minnesota. This was named for a famous Indian chief.