1 9 2 7 . ▁It ▁was ▁officially ▁opened ▁on ▁February ▁ 2 8 , ▁ 1 9 2 8 ▁with ▁much ▁fan fare ▁and ▁several ▁train loads ▁of ▁special ▁guests ▁in ▁attend ance ▁at ▁the ▁East ▁Portal . ▁D & SL ▁locomot ive ▁ 2 0 5 , ▁a ▁ 2 - 6 - 6 - 0 ▁comp ound ▁locomot ive , ▁pulled ▁the ▁first ▁official ▁passenger ▁train ▁through ▁the ▁new ▁tunnel . ▁The ▁M off at ▁T unnel ▁is ▁ 6 . 2 ▁miles ▁long ▁and ▁is ▁the ▁ 6 th ▁largest ▁tunnel ▁on ▁earth . ▁ ▁M ining ▁hold ings ▁Car ib ou , ▁Colorado - ▁Car ib ou ▁mine ▁Cre ede , ▁Colorado ▁C ri pp le ▁Creek , ▁Colorado , ▁Colorado - A na conda ▁and ▁Golden ▁Cy cle ▁Le ad ville , ▁Colorado - B ree ce ▁iron ▁mine , ▁Ma id , ▁Henri ette , ▁Res urre ction ▁and ▁Little ▁Pitts burg ▁Cons olid ated ▁( p urch ased ▁from ▁H . A . W . ▁T abor ) ▁Victor , ▁Colorado ▁White ▁Hills , ▁Arizona - M off at - Root ▁Company ▁- White ▁Hills ▁M ining ▁Company ▁M off at ▁partner ed ▁with ▁Jer ome ▁B . ▁Ch aff ee ▁and ▁H . A . W . ▁T abor ▁in ▁many ▁mines . ▁He ▁had ▁claims ▁in ▁over ▁one ▁hundred ▁Colorado ▁mines ▁at ▁one ▁time ▁or ▁another . ▁M ines ▁belonging ▁to ▁David ▁M off at ▁were ▁involved ▁in ▁at ▁least ▁two ▁significant ▁strik