The Mississippi, Ohio and Black Rivers were overflowing Wednesday morning after a deluge of as much as 15 inches of rain in five days.
In Arkansas, among the dead were at least six people who drowned after their cars were swept away in high water.
Near the swollen Mississippi and Ohio Rivers, emergency officials considered blowing a 2-mile-wide hole in a levee to ease the onslaught of water, but Missouri's attorney general has sued to stop it from happening, saying it would demolish crops and 100 homes.
Homes were still underwater this morning in Missouri after the Black River overflowed its levee in more than 30 different places Tuesday.
The levee breach to the south brought relief to residents in Poplar Bluff because all the flood water is pouring into rural farmland, where there are fewer people.
But it made rescues that much more difficult for authorities.
In downtown Louisville, Ky., roads disappeared, street lamps were submerged and more rain was coming.
A severe storm that swept through Allegan County, Mich., damaged a barn that houses thousands of turkeys.
Part of the barn landed half a mile away at a landscape company where Sue Dykstra works.
"I saw the barn door coming just like breaking off, coming right towards me, so I dodged into the office, dove in there," she said. "And I saw everybody else like huddling under stuff. And said, 'OK, this is a big deal.' Looked outside and that's when everything was going in circles."
Flooding also caused major problems in southern Indiana Tuesday, where, officials say, flooding could take weeks to ease.
In Pike County, sandbags are going up around a power plant and emergency management personnel are asking residents to conserve water, as the Patoka River rises.
"It floods every year. However, this is a little more than what we're used to," Pike County Sheriff Jeremy Britton said. "The levels are probably going tor each record levels."
ABC News' Steve Osunsami and Ryan Creed, ABC News Radio and the Associated Press contributed to this report.