CHICAGO (Reuters) - As floodwaters have surged across the central United States over the past month, the names of the towns in danger have changed: Grand Forks, North Dakota; Cairo, Illinois; Memphis, Tennessee.
But no matter where the waters were rising, the name of the agency scrambling to minimize the damage has remained the same: the U.S. Army Corps of Engineers.
For 75 years now, the Corps -- a part civilian, part military unit of the federal government -- has been the country's official flood-fighting force.
Its work, especially during natural disasters, can be controversial because it often involves picking winners and losers -- as in its decision earlier this month to destroy a Missouri levee and flood farms in that state in order to save towns in Illinois and Kentucky. But its right to do so has been repeatedly affirmed by the nation's courts.
Among the winners this time was Cairo, a historic town at the confluence of the Mississippi and Ohio rivers, where thousands of former slaves settled before and after Emancipation.
Among the losers was Kevin Nally, a 40-year-old farmer near Charleston, Missouri, who had 80 acres of wheat in the ground that washed away when the Corps blasted the levee, opened the floodway and inundated 130,000 acres of surrounding farmland.
So far, the intentional breach seems to have averted a greater disaster: levees are holding despite record river gauge readings from Cairo to Natchez, Mississippi.
"The system is working as designed right now," said Corps spokesman Curry Graham. "It seems to be mitigating some of the effects of what we saw back in 1927."
Not all the choices the Corps has made in its 209-year history have worked out so well.
Its long support of a "levee-only" approach to flood control along the Mississippi, for instance, is thought to have contributed to catastrophic flooding in 1927 that killed as many as 500 people and left another 500,000 homeless.
In the Florida Everglades, many environmentalists say the Corps' flood control efforts following two hurricanes in the late 1920s contributed to the ecosystem's woes.
Founded in 1802, the Corps is a curious hybrid, reporting to both Congress and the Department of Defense. Its work includes everything from dredging U.S. waterways to building blast-resistant military facilities in Afghanistan and Iraq.
Most of its 36,000 employees are civilians. But its head is a uniformed member of the military. As the Mississippi and its tributaries rise past flood stage every spring, swollen by the seasonal snow melt and rain, it's almost always a colonel or a general coordinating the response from atop a levee.
The decisions these officers make are not always popular with civilians. But Washington's role in flood control has been controversial from the country's start, with politicians from states far from the dikes and danger viewing the expense as a local burden their constituents need not subsidize.
In 1936, Congress ended the debate. It said flood control was a legitimate activity of the federal government and put the Corps in charge. Since then, it has fought nearly a dozen major floods on the Mississippi alone.
But the Corps was working on the nation's waterways, eliminating snags, sandbars and other navigational hazards for more than a century before the 1936 law was passed.
Its remit to improve Mississippi navigability began in 1824. It became the custodian of the nation's rivers and canals because early U.S. history, particularly Britain's blockade of ports during the War of 1812, had highlighted the connection between inland navigation and national defense.
Its responsibilities grew partly because West Point, the Army academy originally run by the Corps, was the country's only engineering school until the 1830s.
"The Army had the expertise," said John Lonnquest, the Corps' chief historian. "So when big-scale engineering needed to be done, they turned to us."
Today, the Corps helps maintain two lines of defense against flooding: a vast network of levees, which hold the water back; and a sprawling system of spillways, floodways and reservoirs, which divert waters into portions of the bottomlands when the levees are in danger.
In the 1930s, it undertook a massive dredging of the Mississippi between Memphis and Natchez to radically increase the rate at which floodwaters cleared the river basin and entered the Gulf of Mexico.
Charles Camillo, the official historian of the Corps' Mississippi Valley Division, thinks those channel improvements are a big reason why this year's flooding -- which he calls extraordinary -- isn't causing the damage seen in 1927.
"We're seeing the positive effects of that channel improvement program right now," he said.
"They dredged like crazy to improve the alignment of the river and to lock it into place so that the river would carry more water and get it out to sea faster. And it's working. The system's under incredible pressure. But it's working."
Reporting by James B. Kelleher; Editing by Jerry Norton