The Midwest sometimes struggles with marketing -- who's in the Midwest, who's not, why does Ohio sound so much like Iowa? So we're not doing ourselves any favors when we're sticking parts of some states in other states.
Carter Lake, Iowa, for instance, is actually in Nebraska. So if you're heading to Omaha's airport from Council Bluffs, you'll leave leave Iowa crossing the Missouri River, then enter Iowa again near the Hampton Inn, then leave Iowa again right before the airport.
According to the city's website: in March of 1877, there was a major flood that changed the flow of the Missouri River, thus creating an oxbow lake. Since state boundaries usually follow the general course of a river, there was a dispute for some time whether Carter Lake should belong to Iowa or Nebraska. In 1892, the Supreme Court ruled that Carter Lake belonged to Iowa.
Slightly adding to the confusion, when you Google Carter Lake, Iowa, it gives you a picture of Crater Lake. So if you are heading to Carter Lake expecting to see the vista below, uhhhhhhhh, prepare to be disappointed.