In Mississippi, Louisiana, and Arkansas, authorities and residents braced for the days ahead.
"I went through (Hurricane) Katrina," said Lynn Magnuson, a New Orleans resident. "I would not wish flooding on anyone, and this city is the last place on Earth that needs any more high water."
The river crested Tuesday at Memphis, just short of a record set in 1937.
The river in Memphis measured 47.8 feet Tuesday night, according to the National Weather Service.In Natchez, Mississippi, the river surpassed its record early Wednesday, exceeding 58 feet. Forecasts predict the river will crest in Natchez on May 21 at an overwhelming 64 feet.
Mississippi has already had to close some of its casinos at Tunica, a key economic driver in that part of the state, as flood waters seeped in.
About 600 people in the Tunica community of Cutoff have been driven from their homes, said Larry Liddell, a county spokesman.
"We're just watching and waiting," he said.
In Louisiana, Gov. Bobby Jindal said as many as 3 million acres could be affected by the flooding. Some 500 National Guard members have been mobilized so far and 21 parishes have issued emergency declarations.
The river's crest is expected to begin arriving in Louisiana next week. Flooding is expected to be a major setback in the southern part of the state. (read more)