North Dakota has been declared a federal disaster area by US President Barack Obama because of record spring flooding across the mid-Western state.
Floodwaters from the Red River, which is expected to peak later this week, have closed roads and bridges.
National guardsmen and volunteers are reinforcing flood defences.
The rising waters are also affecting the neighbouring state of Minnesota which, like North Dakota, borders the Red River on its route towards Canada.
A blizzard has brought snow and freezing rain to North Dakota and high winds have knocked out the electricity supply to some towns in the state.
Hundreds of miles of highways and roads have been blocked in North Dakota and the neighbouring states of Montana, Wyoming, South Dakota and Nebraska.
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