"Their misfortune had been our fortune. I'd rather it hadn't come at the expense of others. But it is what it is," Steve Cirinna of the Lee County Emergency Management Agency said of the levee breaches, which lowered the river.

The slow-rolling disaster, the worst flooding in the Midwest in 15 years, has swamped vast sections of the US farm belt and forced tens of thousands of people from their homes.

LeRoy Lippert, chairman of emergency management committee for Des Moines County, Iowa, said volunteers and aid workers in the town of Burlington filled 2.5 million sandbags in the past week before the river crested.

"All systems are holding right now. We're in a watch and wait mode with our levees. The situation has stabilized in the last 24 hours," Lippert said.

"The best news is that we're not getting any rain, that would be utterly devastating if we got heavy rain now."

The Army Corps of Engineers, which operates river locks and dams, said 19 levees along the Mississippi had failed with the latest levee breaks near Meyer, Illinois, and north of St. Louis, Missouri.

"They were lower level agricultural levees," said St Louis district Corps spokesman Alan Dooley. "We're also watching another seven levees that may overtop in the next couple of days ... all agricultural levees."

The Corps has identified 26 levees protecting about 285,000 acres of cropland that were already under high water or at high risk of flooding. Another seven were seen as potential risks.

FERTILE FARMS

Among the most fertile farms in Iowa and Illinois have land that lies in the Mississippi River's vast flood plain.

"Some of the richest farmland is to be found between the river and the bluff and we aim to protect it," said Lippert.

Estimates are that 5 million acres across the Midwest have been ruined and will not produce a crop this year.

That has sent US grain and livestock prices soaring, the latest inflation jolt for an economy already struggling to absorb record oil and energy prices.

Iowa and Illinois usually produce one-third of all US corn and soybeans. So expected smaller crops from the main sources of livestock feed, renewable fuels like ethanol, starch and edible oils has sent commodity prices to record highs.

Chicago Board of Trade corn prices, the world benchmark, hit a record of US$8.07 a bushel in overnight trading.

The worst flooding has struck Iowa but evacuations have also affected flooded sections of Indiana, Wisconsin, Illinois, and Minnesota in what authorities predict will be a multi-billion dollar disaster.

Weather forecasters said thunderstorms may return to Iowa and Illinois on Thursday.

In Fort Madison, a few sightseers skirted the flooded riverfront, snapping photographs of the raging river. Across the river in Lomax, Illinois, a cafe put out a sign: "Free coffee for flood workers."

In the farm fields around Dallas City, Illinois, the scene resembled a large lake, bright sunshine glinting off large grain silos surrounded by water. (Additional reporting by Lisa Shumaker, Peter Bohan and Christine Stebbins in Chicago; Debbie Charles in Washington; Writing by Andrew Stern; Editing by Chris Wilson)