Sandbagging was under way in Burlington, a key rail hub, to build the city's levee system and protect it from the river; 350 people had been evacuated.
Two more deaths were reported, bringing the state's death toll from flooding to five. A 35-year-old man apparently drowned in Iowa River floodwaters near Wapello, and a woman was killed near New London when her stopped car was hit by a National Guard bus involved in flood duty. Two Wisconsin deaths also were linked to flooding during the weekend.
"It's likely that we will see major and serious flooding" in the southeast, Gov. Chet Culver said. "We are taking precautionary steps, we are evacuating where necessary, but that is going to be the next round here."
The American Red Cross said Monday that its disaster relief fund has been completely spent, and the agency is being forced to borrow money to help flood victims.
Meanwhile in Iowa City, Poppy Crum was lucky enough to be allowed to return to her childhood home on Monday, but as she approached in a rowboat, CBS News Correspondent Hari Sreenivasan reports, she found all her childhood memories had dissolved in the floodwater.
"You watch things from your childhood just sort of disintegrate in the water," Crum said. "By the time I got in here, it was already a foot."
Elsewhere in the soaked Midwest, National Guard soldiers hoped to fill about 500,000 sandbags by Monday to fortify levees along a 15-mile stretch of the Mississippi River in western Illinois, near the city of Quincy, and flood waters began to recede in parts of western Michigan.
The Iowa River's crest arrived early and lower than expected, possibly because of a number of levee breaches downstream that opened the channel, the National Weather Service said. Culver called word of Iowa City's crest "a little bit of good news," but cautioned that the situation was still precarious.
President George W. Bush will visit the Midwest on Thursday to inspect flood damage, the White House said Monday as the president wrapped up a weeklong trip in Europe. White House press secretary Dana Perino said the places the president would visit had not been chosen.
The flooding has raised fears of a sharply smaller U.S. corn crop in a region critical to production, driving grain prices higher and stoking concerns about another spike in world food prices.
The U.S. government will report June 30 on how many acres have been lost to flooding, but a survey in Farm Futures magazine estimated that flooding could claim 3.3 million acres - or nearly 4 percent of the expected crop.
With much of Cedar Rapids still off limits, thousands of home-owners are so desperate to see if they have anything left, CBS News Correspondent Cynthia Bowers reports.
"It's my property, I own it, why can't I go in and inspect it," wondered Cedar Rapids resident Rick Blazek.
Police drew their guns and arrested a man who tried to run their roadblock and get home, Bowers reports. The rest found out that even though the water's gone down, the barricades have not.
"I want to go into my house, half my stuff could be gone," said Joan Harwood.
A lucky few managed to get in to flood ravaged neighborhoods late yesterday but authorities now say it's too dangerous and put the streets back on lockdown.
That doesn't hold water with folks like Harwood, whose entire future is tied up in her house.
"You get everybody's hopes up that we're gonna let you into your house and then you pull the rug out from underneath you again," Harwood.
Most say going home is a risk worth taking.
"Should have been in there cleaning up two days ago, it don't make sense," said Larry Van Deusen. "Every day that you're not in there, that mold is growing. It's stupid."
The flooding has also heightened health concerns, with emergency officials warning of toxins in the water from sewage, farm chemicals, refuse and dead animals. "If you drink this water and live, tell me about it. You have no idea. It is very, very wise to stay out of it. It's as dangerous as anything," said LeRoy Lippert, chairman of emergency management and homeland security in Des Moines County.
In the university town of Iowa City, which has a population of about 60,000, about 5,000 people were evacuated on Sunday, and 400 homes had suffered significant damage. But the river was expected to begin receding Monday night as the threat of new flooding flowed southeast.
The University of Iowa campus in Iowa City reported no new damage overnight after floodwaters hit 16 buildings through the weekend, including one designed by acclaimed architect Frank O. Gehry. Some buildings had as much as 8 feet of water inside.
Early Monday, more than 38,000 residents in 26 Iowa communities had been evacuated from their homes, said Kevin Baskins of the state Emergency Operations Center. Most of those - 25,000 - were in hard-hit Cedar Rapids, further north, which was hit last week.
Eight people were pulled Sunday from the flooded Des Moines River in Ottumwa after their boat capsized, police Chief Jim Clark said. The boaters were exhausted, cold and showing some confusion. Four were being treated for hypothermia, Clark said.
The threat to southeast Iowa was already taking shape, though the Mississippi River is days from cresting. State officials girded for serious flooding threats, sending 500 National Guard troops to Burlington.
The Iowa River breached levees in the town of Columbus Junction on Saturday evening, leaving much of the downtown, including a medical center, senior center, water plant and a couple dozen other businesses under about 10 feet of water.
In Cedar Rapids, residents waited hours to get their first up-close look since flooding hammered most of the city last week.
The city's municipal water system was back to 50 percent of capacity Sunday, a big victory after three of the city's four drinking water collection wells were contaminated by murky, petroleum-laden floodwater. That contamination had left only about 15 million gallons a day for the city of more than 120,000 and the suburbs that depend on its water system.