The flooding across a predominantly rural part of the country was caused by a big storm last week and rapid snow melt that swelled streams and rivers in large swaths of the middle of the United States, and sent gushing water over levees.
Hundreds of homes and businesses were inundated, roadways damaged, and bridges washed away in several states, with much of Nebraska and parts of Iowa hardest hit.
Officials also were concerned about crop and livestock losses at farms, Press TV reported.
"This past week will forever be remembered for the historic, devastating flooding our state experienced," Nebraska Governor Pete Ricketts said in a statement.
"In scope of reach, we believe it is the most widespread natural disaster in our state's history."
Vice President Mike Pence headed to Nebraska on Tuesday to survey the damage, where nine shelters remained open for displaced residents.
Iowa Governor Kim Reynolds said she and Ricketts would be seeking expedited federal funds to repair roads and other infrastructure. Reynolds has declared 41 Iowa counties disaster areas.
"We're continuing to work with local officials to assess the flood damage," she told a news conference.
While waters were receding in some areas, the National Weather Service (NWS) forecasted flooding would persist in parts of eastern Nebraska and western Iowa.
"Major to historic and catastrophic flooding will continue across parts of the Missouri and Mississippi River Basins," the NWS said in an advisory.
Nebraska officials estimated that damage to public and private property topped $600 million. The Nebraska Farm Bureau, a group representing farmers, expected crop and livestock losses around $1 billion.
"We won't know of course for a little while what the losses are, but I would not be surprised to see the losses to go over a billion dollars for agriculture in Nebraska," the group's president Steve Nelson told The Weather Channel.
Dozens of cities and counties in Nebraska had declared states of emergency. Some residents in small towns and rural areas were surrounded by waters and cut off, while others evacuated to shelters.
Reynolds said two-thirds of the small town of Hamburg, with a population of approximately 1,000, was destroyed.
Two people were killed in Nebraska last week due to the raging flood waters, while a motorist died in Iowa after his vehicle was swept away.
A third of a US Air Force Base in Nebraska was overcome with floodwaters, and was not expected to be dry again until Thursday.