▁instead ▁of ▁Colorado . ▁Between ▁the ▁spring ▁of ▁ 1 9 7 1 ▁and ▁the ▁summer ▁of ▁ 1 9 7 2 , ▁passengers ▁travel ing ▁between ▁Chicago ▁and ▁Oak land ▁would ▁have ▁to ▁travel ▁on ▁two ▁different ▁trains : ▁the ▁Den ver ▁Ze ph yr , ▁which ▁operated ▁daily ▁between ▁Chicago ▁and ▁Den ver , ▁and ▁the ▁City ▁of ▁San ▁Francisco , ▁which ▁operated ▁three ▁times ▁a ▁week , ▁between ▁Den ver ▁and ▁the ▁San ▁Francisco ▁Bay ▁Area . ▁Event ually , ▁however , ▁after ▁several ▁false ▁starts , ▁Am tra k ▁cons olid ated ▁the ▁two ▁trains ▁into ▁one , ▁dub bed ▁the ▁San ▁Francisco ▁Ze ph yr , ▁hom age ▁to ▁both ▁the ▁California ▁Ze ph yr ▁and ▁the ▁San ▁Francisco ▁Chief , ▁between ▁Chicago ▁and ▁Oak land . ▁The ▁Rio ▁Grande ▁continued ▁to ▁operate ▁the ▁Rio ▁Grande ▁Ze ph yr ▁between ▁Den ver ▁and ▁Og den . ▁ ▁In ▁ 1 9 8 3 ▁the ▁D & R G W ▁elected ▁to ▁join ▁Am tra k , ▁cit ing ▁increasing ▁losses ▁in ▁passenger ▁operations . ▁Am tra k ▁re - rout ed ▁the ▁San ▁Francisco ▁Ze ph yr ▁over ▁the ▁D & R G W ' s ▁M off at ▁Sub div ision ▁between ▁Den ver ▁and ▁Salt ▁Lake ▁City , ▁its ▁original ▁preference ▁from ▁ 1 9 7 1 . ▁The ▁change ▁was ▁scheduled ▁for ▁April ▁ 2 5 , ▁but ▁a ▁mud slide ▁at ▁Th ist le , ▁Ut ah ▁closed ▁the ▁line ▁and ▁delayed ▁the ▁change