From the abstract: "The floods of June 1954 were the greatest known on the Iowa River above Eldora, on the Des Moines River below Fort Dodge to Des Moines, and on the Rock and the Little Sioux Rivers. Near-record floods occurred on the Des Moines River at and upstream from Fort Dodge, and on the Cedar River and tributaries upstream from Waterloo. Flood damage amounted to nearly $28 million. Much urban damage occurred; however the above total consisted mainly of agricultural damage with an estimated 725, 000 acres of cropland in 26 northern counties of Iowa under water during the first 3 weeks in June."
Geological Survey Water-Supply Paper 1370-A
United States Geological Survey: https://www.usgs.gov/