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Carter Lake, Iowa
An Iowa city on the Nebraska side of the Missouri River
Carter Lake is a city of about 3,800 people that belongs to Iowa but sits on the Nebraska side of the Missouri River, almost entirely surrounded by Omaha. Until 1877 the land was ordinary Iowa riverbank. Then a March flood shoved the Missouri about a mile and a quarter to the southeast, cutting off a loop of the old channel. The abandoned bend became an oxbow lake, named Carter Lake, and the neighborhood beside it was left on the wrong side of the river.
Nebraska argued that the land should follow the river. In Nebraska v. Iowa (1892), the U.S. Supreme Court disagreed, ruling that a sudden change of course, unlike slow erosion, does not move a state boundary. Carter Lake stayed in Iowa, and the case became a cornerstone of American boundary law. Today the city wraps around the south and west sides of Omaha's Eppley Airfield, so travelers headed for a Nebraska airport often pass an Iowa welcome sign on the way.