 The cost was $ 490 million ( equivalent to $ 800 million today ) to build 12 miles ( 19 km ) , 40 times the average cost per mile predicted by the planners of the Interstate Highway system . This figure exceeded that of Interstate 15 through the Virgin River Gorge , which was previously proclaimed the most expensive rural freeway in the United States . The construction of I @-@ 70 through Glenwood Canyon earned 30 awards for the Colorado Department of Transportation , including the 1993 Outstanding Civil Engineering Achievement Award from the American Society of Civil Engineers . At the dedication it was claimed that I @-@ 70 through Glenwood Canyon was the final piece of the Interstate Highway System to open to traffic . For this reason , the system was proclaimed to be complete . However , as of 2009 , at least two sections of the original Interstate Highway System have not been constructed : a section of Interstate 95 in central New Jersey , and a section of I @-@ 70 in Breezewood , Pennsylvania . 
