A swollen Mississippi River flooded surrounding lands across the Upper Midwest Wednesday, halting trains and forcing hundreds of people to evacuate their homes.

A 403-mile stretch of the Mississippi from Minneapolis to Muscatine, Iowa, is closed to boat and barge traffic. Nine counties in western Wisconsin are under a state of emergency and a disaster proclamation has been posted for 10 Iowa counties.

Fed by melting snow and rain, the lifeline of the Midwest put dikes to the test in four states. In the lowlands of Wisconsin and Iowa, hundreds had to leave their homes while volunteers and prisoners in Hampton, Ill., worked side by side to sandbag homes along the river. In Minnesota, contractors rushed to strengthen a weakened earthen dam on a tributary.

On French Island, near La Crosse, Wis., Rep. Ron Kind, his wife and two children fled from the four feet of water invading their home. The Mississippi was expected to crest 4 ½ feet above the 12-foot flood stage at La Crosse on Wednesday — lower than previously predicted.

"We were completely engulfed and surrounded by the Mississippi," the congressman said after a canoe trip to check on the house and his neighbors.

Just upstream, in Fountain City, the main highway remained closed. School officials postponed the prom scheduled for Saturday at the high school and called off classes through Thursday.

The Mississippi rose above 23 feet at St. Paul, Minn., for the first time since the 1960s. Four city parks and the downtown airport for small planes were under water.

One man was missing after he and a companion drove past barricades onto a flooded highway near Minneapolis earlier this week.

At Appleton, Minn., contractors were sent to shore up the Marsh Lake Dam on the upper Minnesota River. The earthen dam had been weakened by erosion and battered by huge chunks of ice.

If the dam were to collapse, officials said, it could raise water levels downstream at Montevideo and Granite Falls by up to 1 ½ feet. However, the river was already receding in both communities and local authorities said dikes should be able to handle any increase.

Amtrak suspended its Empire Builder train service between Minneapolis-St. Paul and Chicago because of high water on the tracks, and put passengers on buses. About 200 people were affected Monday, said Amtrak spokesman Kevin Johnson.

Burlington Northern Santa Fe's main rail line from the Twin Cities to Chicago remained closed Tuesday because the Mississippi was over the tracks at several locations. A spokesman said trains were being rerouted but faced delays of up to 48 hours.

More than 200 of the 300 families living on Abel-Essman Island, in the Mississippi near Guttenberg, Iowa, abandoned their homes Monday and the only road to the island was closed when the water reached 19 feet, or 4 feet above flood stage. The river is expected to crest there Friday at about 21 feet.

Several Mississippi River communities in Missouri were keeping an eye on water levels but expected no serious damage. No flooding was expected in St. Louis because of levees, floodwalls and the city's geography, National Weather Service hydrologist Scott Dummer said.