 The first Colorado portion of I @-@ 70 opened to traffic in 1961 . This section bypassed and linked Idaho Springs to the junction where US 6 currently separates from I @-@ 70 west of the city . The majority of the alignment through Denver was completed by 1964 . The Mousetrap reused some structures that were built in 1951 , before the formation of the Interstate Highway system . The last piece east of Denver opened to traffic in 1977 . 
