What happens when they moved the river?

You find some buried shipwrecks.
One such place was near Parkville, a few miles north east of Kansas City. It was here in 1856 that the Arabia sank after hitting a snag of a sycamore tree, sinking in minutes. As the course of the river was altered decades later, the steamboat became preserved not under the muddy waters of the Missouri, but in a corn field. 
It's incredible how well-preserved this stuff is.