 The U.S. Department of Transportation ( USDOT ) lists the construction of I @-@ 70 among the engineering marvels undertaken in the Interstate Highway system , and cites four major accomplishments : the section through the Dakota Hogback , Eisenhower Tunnel , Vail Pass and Glenwood Canyon . The Eisenhower Tunnel , with a maximum elevation of 11 @,@ 158 feet ( 3 @,@ 401 m ) and length of 1 @.@ 7 miles ( 2 @.@ 7 km ) , is the longest mountain tunnel and highest point along the Interstate Highway System . The portion through Glenwood Canyon was completed on October 14 , 1992 . This was one of the final pieces of the Interstate Highway System to open to traffic , and is one of the most expensive rural highways per mile built in the United States . The Colorado Department of Transportation ( CDOT ) earned the 1993 Outstanding Civil Engineering Achievement Award from the American Society of Civil Engineers for the completion of I @-@ 70 through the canyon . 
