People living along the upper Mississippi River saw floodwaters begin to crest on Monday and the threat of inundation start to recede. (Spencer Green/Associated Press)

Floods along the upper Mississippi River are still well above the banks of the fabled waterway, but soggy earthen levees and hastily built sandbag barriers seemed to be holding Monday, officials and beleaguered residents said.

Forecasters said the rain-swollen river appeared to have crested sometime on Sunday in northern Missouri, easing pressure on communities and states downstream.

"It's quieter compared to earlier this week," said the head of emergency management for the riverside town of Louisiana, Mike Lesley, where sandbagging has largely ceased. This past weekend, he said, "I actually got some sleep."

The river started cresting Sunday at Canton, Mo., not far from the Iowa state line, where the worst flooding took place along Mississippi tributaries earlier this month.

Next, according to federal forecasters, crests were expected Monday near Clarksville. Mo.

In Mark Twain's birthplace, Hannibal, emergency management director John Hark said he was confident the town's levees would hold as the river begins to recede.

Further downstream in the Illinois communities of Winfield and Grafton, forecasters said the Mississippi would continue to rise Monday and Tuesday before cresting on Wednesday, but barriers were holding.

A reminder the threat had not passed came Sunday in Lincoln County, Mo., where a levee was overwhelmed by rising waters that flooded about 400 hectares of farm land and several homes.

Rural areas worst affected

Devastation from nearly a month of severe weather and flooding is widespread. Thousands have been forced from their homes across six states, and 24 deaths and 150 injuries have been directly blamed on the disaster.

Rural areas such as Lincoln County suffered the worst. More than 300 homes were flooded after more than 90 per cent of the county's levees were inundated.

The heavy rains and intense storms that sparked the flooding in early June have disappeared from weather forecasts with just seasonal rainfalls now predicted, said National Weather Service meteorologist Ben Miller.

The flooding also damaged several grain crops in Iowa, Illinois and other states.

More than a million hectares of corn and soybeans have been ruined, agriculture officials said, sending prices soaring on commodities markets.

The U.S. government says it’s making more than $4 billion in disaster relief funding available for the cleanup.

With files from the Associated Press