Minot, located in the north-central part of the state, is the fourth-largest city in North Dakota.
The swollen Souris River flows straight through the city and is expected to overwhelm area levees, said Cecily Fong, spokeswoman for the North Dakota Department of Emergency Services.
"It's really historic proportions of water," Fong said late Tuesday night.
The evacuation order covers a third of the community's population, Fong said. Residents have until 6 p.m. Wednesday to leave.
"The river is rising faster than expectations, so they (city officials) are kind of scrambling to shore up levees and do what they can," Fong said.
The National Weather Service has forecast record flooding and urged anyone living in the affected areas to prepare immediately for oncoming floodwaters. Heavy area rains and dam releases are causing the river to swell at Minot.
"The current best estimate for when water will overtop the lowest dikes in the Minot area is sometime on Thursday afternoon. However, a Wednesday night or early Thursday timeframe cannot be ruled out as the dikes become more stressed due to rising water," the weather service said.
The river at Minot, which currently stands at close to 1,555 feet above sea level, is forecast to rise to 1,559 feet on Friday or Saturday -- which would be a new record. The river hit 1,558 feet above sea level in 1881.
The Souris River looks like a "U." It swoops in and out of North Dakota from Canada.
