 On both sides of the state , the respective river crossings opened to traffic nearly two years later than the connecting highways . Near LeClaire , the Fred Schwengel Memorial Bridge over the Mississippi River opened in 1966 after the highway had been completed to US 67 , which runs at the foot of the bridge , in 1964 . The center span of the Mississippi River bridge was installed on June 29 , 1966 . The 237 @-@ foot @-@ long ( 72 m ) , 520 @-@ short @-@ ton ( 470 t ) piece was floated into place by barge . In Council Bluffs , the Missouri River crossing opened on December 15 , 1972 , while the approach to the bridge opened in November 1970 . The Missouri River bridge 's completion marked the end of the 14 years it took to construct Interstate 80 . 
