But even as the water jeopardized scores of additional homes and businesses, officials said the damage could have been worse if the federal government had not taken steps to clear flood-prone land after historic floods in 1993.
The flooding, which has claimed at least five lives in Iowa and two in Wisconsin over the past week, has resulted in thousands being forced from their homes.
On Tuesday, the flooding halted car travel over two bridges linking Illinois and Iowa and covered the tiny farming community of Gulfport and the surrounding area with three metres of water.
"I'm not going back after this one," 83-year-old Lois Russell said as she watched water surround her house near Gulfport. It was the third time she had fled her home because of flooding since 1965.
"It was a good place to raise my seven kids," she said, crying. "I know I haven't lost anything that feels important because I have a big family."
The area was inundated after the Mississippi River, the US' main internal commercial waterway, broke through a levee near Gulfport. Authorities had to rescue at least six people by helicopter, boat and four-wheeler.
President George W. Bush, whose administration was sharply criticized for its handling of the situation in the wake of the 2005 Hurricane Katrina along the US Gulf Coast, was briefed on the damage and planned to visit the area on Thursday.
A 6.4-metre railway outside Gulfport broke in four sections on Tuesday night, sending flood waters into the evacuated town. Henderson County Sheriff Mark Lumbeck said Gulfport has about three metres of water.
Preliminary estimates were that the flooding has caused more than US$1.5 billion ($NZ2 billion) in damage in Iowa, and that figure will undoubtedly rise as the high water moves downstream.
Still, officials said the cost would have been even higher if the federal government had not purchased low-lying land after the 1993 deluge, which caused US$12 billion in damage.
Since then, the government bought out more than 9,000 homeowners, turning much of the land into parks and undeveloped areas that can be allowed to flood with less risk. The Federal Emergency Management Agency has moved or flood-proofed about 30,000 properties.
The effort required whole communities to be moved, such as Rhineland, Missouri, and Valmeyer, Illinois.
In Iowa, FEMA spent US$1.6 million to buy out residents of Elkport, population 80, and then knock down the village's remaining buildings. Some residents moved to Garber, Elkport's twin city across the Turkey River, but others abandoned the area.
On Tuesday, flooding remained far more serious in parts of southeast Iowa, where the Mississippi River had yet to crest.
People were urged to evacuate an area near Gulfport as floodwaters threatened about 31 square kilometres of farmland. Henderson County Deputy Sheriff Donald Seitz said a major highway could be under three metres of water by midday Wednesday.
On the Iowa side of the river, a sandbagging operation was moved south to the outskirts of Burlington after floodwaters streamed across state Highway 99.
Officials were also concerned about the integrity of a levee that protects a drainage area south of Oakville.
Jeff Campbell, a farmer carrying sandbags on his four-wheeler, said he spotted pigs swimming away from a flooded hog farm near Oakville. They were climbing a levee, poking holes in the plastic that covered it, he said.
One tired pig was lying at the bottom of the levee "like a pink sandbag," Campbell said.
Reports of raw sewage and farm runoff in floodwaters raised concerns about public health. But experts said most people are smart enough to avoid the tainted water.
The rising water forced the closure of the Mississippi bridge in Burlington and stopped car traffic on the bridge in Fort Madison. The bridge's railroad tracks remained open. A bridge downriver in Keokuk also remained open.
To the north in Cedar Rapids, floodwaters had dropped enough that officials let hundreds of people return to their damaged homes and businesses.
"It's obviously much more shocking when you walk in the door for the first time and see what happened," said Amy Wyss, watching sullenly as a giant blower was used to dry out her upscale wine bar, Zins. "I don't think you can be prepared for this, even if you think you are."
The National Weather Service expects crests this week along some Mississippi River communities near St. Louis to come close to those of 1993. The river at Canton, Missouri, could reach 8.44 metres on Thursday, just shy of the 8.5-metre mark of 1993 and more than four metres above flood stage.
Crests at Quincy, Illinois, are expected to climb to about 4.5 metres above flood stage, narrowly short of the high water from 15 years ago. In Hannibal, Missouri, the river is projected to crest at 9.7 metres, matching the 1993 record.
In St. Louis, the Mississippi is projected to crest on Saturday at 12.1 metres, about three metres above flood stage but still than in 1993.
