ope ▁Valley ▁begins ▁as ▁Ant el ope ▁W ash ▁in ▁northern ▁N ye ▁County ▁between ▁the ▁Mon itor ▁Range ▁and ▁the ▁Ant el ope ▁Range . ▁The ▁head w aters ▁of ▁the ▁valley ▁begin ▁as ▁a ▁narrow ▁mountain ▁valley ▁on ▁the ▁north ▁side ▁of ▁a ▁water ▁divide ▁about ▁ ▁south ▁of ▁the ▁N ye - E ure ka ▁line . ▁ ▁Ant el ope ▁Valley ▁broad ens ▁to ▁about ▁ ▁wide ▁at ▁about ▁ ▁to ▁the ▁north . ▁ ▁There after ▁Ant el ope ▁Valley ▁mer ges ▁with ▁the ▁Mon itor ▁Valley ▁from ▁the ▁west ▁and ▁the ▁Kob eh ▁Valley ▁from ▁the ▁north ▁to ▁become ▁a ▁broad ▁bas in ▁between ▁the ▁Mon itor ▁and ▁Sim pson ▁Park ▁ranges ▁to ▁the ▁west , ▁Roberts ▁Mountains ▁to ▁the ▁north ▁and ▁the ▁Ant el ope , ▁Fish ▁Creek ▁and ▁Mountain ▁Boy ▁ranges ▁to ▁the ▁sout heast . ▁The ▁combined ▁valle ys ▁form ▁a ▁broad ▁bas in ▁about ▁ ▁in ▁diameter . ▁ ▁The ▁isolated ▁L one ▁Mountain ▁within ▁the ▁sout he astern ▁portion ▁of ▁the ▁valley ▁separ ates ▁Ant el ope ▁and ▁Kob eh ▁valle ys . ▁L one ▁Mountain ▁is ▁about ▁ ▁in ▁diameter ▁at ▁its ▁base ▁and ▁reaches ▁an ▁elev ation ▁of ▁ ▁at ▁its ▁peak . ▁This ▁is ▁about ▁ 1 9 0 0 ▁feet ▁above ▁the ▁valley ▁floor . ▁ ▁Stream ▁d rain age ▁from ▁Ant el ope ▁W ash ▁and ▁from ▁a ▁number ▁of ▁streams ▁from ▁the ▁Roberts ▁Mountains ▁merge ▁to ▁the ▁south west ▁of ▁L one ▁Mountain ▁to ▁form ▁Sl