Although the Missouri River generally is the boundary between Iowa and Nebraska, the river in 1877 had avulsed one of its bends, cutting off the land that later became the city of Carter Lake on the western side. The Supreme Court six years earlier had mentioned the circumstances of Carter Lake when it ruled on a boundary dispute between the two states in Nebraska v. Iowa, 406 U.S. 117 (1972).
The Missouri River's course in 1877 shifted, creating land that became Carter Lake on the western side of the river, which was a result of a bend being severed. This event was previously considered by the Supreme Court when it ruled on a boundary dispute between Iowa and Nebraska in the case of Nebraska v. Iowa, 406 U.S. 117 (1972).