Rising water from the Cedar River forced the evacuation of a downtown hospital Friday after residents of more than 3,000 homes fled for higher ground. A railroad bridge collapsed, and 400 city blocks were under water.

In Des Moines, 100 miles to the southwest, officials issued a voluntary evacuation order for much of downtown and other areas bordering the Des Moines River. Mayor Frank Cownie said the evacuations were an attempt "to err on the side of citizens and residents."

Des Moines is Iowa's capital and largest city, with about 190,000 residents. But the hardest-hit was Cedar Rapids, a city of 124,000 people.

Gov. Chet Culver declared 83 of the state's 99 counties to be state disaster areas, and nine rivers were at or above historic flood levels. Elsewhere in the upper Midwest, rivers and streams tipping their banks forced evacuations, closed roads, and even threatened drinking water.

Dave Koch, a spokesman for the Cedar Rapids fire department, said the river will crest Friday at about 31.8 feet. It was at 30.9 feet early in the morning. In a 1993 flood, considered the worst flood in recent history, it was at 19.27 feet.

The weather conditions that triggered the floods were the same as those in 1993: hot air from a ridge of high pressure on the East Coast colliding with cooler air from the West Coast, according to Ken Kunkel, interim director of the Illinois Water Survey.