 Continuing east , the two routes follow a due @-@ east section of highway , where they pass Earlham . Near the CR F90 / CR <unk> interchange , they start heading northeast towards Des Moines . At De Soto , US 6 splits away from I @-@ 80 at the interchange with US 169 . Tourists who want to see the covered bridges of Madison County ( made famous by the book The Bridges of Madison County ) and the birthplace of John Wayne , are directed to follow US 169 south to Winterset . Between De Soto and Van Meter , the interstate crosses the middle and north branches of the Raccoon River , which converge just south of the crossing of the North Raccoon . 
