Iowa Governor Kim Reynolds has asked the federal government for $4 billion to help the state recover from a wind storm.
The damage to cities and rural towns left more than half a million homes and businesses without power and at least three people died.
Winds gusted to 160 kilometres per hour as the storm, known as a derocho, moved from eastern Nebraska, across Iowa and into Chicago
It flattened crops on 37.7 million acres, including 14 million in Iowa, the Iowa Soybean Association said on Friday.
There could be claims from 58,000 crop insurance policies with a liability of around $6 billion in Iowa, including $1.86 billion for soybeans, the Iowa Soybean Association said.
