ds ▁are ▁in ▁the ▁process ▁of ▁being ▁created ▁or ▁have ▁been ▁created ▁in ▁state ▁par ks ▁and ▁national ▁par ks , ▁and ▁on ▁private ▁ran ches , ▁with ▁individuals ▁taken ▁from ▁the ▁existing ▁main ▁' found ation ▁her ds '. ▁ ▁An ▁example ▁is ▁the ▁Henry ▁Mountains ▁b ison ▁her d ▁in ▁Central ▁Ut ah ▁which ▁was ▁founded ▁in ▁ 1 9 4 1 ▁with ▁b ison ▁that ▁were ▁re located ▁from ▁Y ellow stone ▁National ▁Park . ▁This ▁her d ▁now ▁numbers ▁approximately ▁ 4 0 0 ▁individuals ▁and ▁in ▁the ▁last ▁de cade ▁steps ▁have ▁been ▁taken ▁to ▁expand ▁this ▁her d ▁to ▁the ▁mountains ▁of ▁the ▁Book ▁Cl iffs , ▁also ▁in ▁Ut ah . ▁ ▁One ▁of ▁the ▁largest ▁priv ately ▁owned ▁her ds , ▁number ing ▁ 2 , 5 0 0 , ▁in ▁the ▁US ▁is ▁on ▁the ▁T all gr ass ▁Pra irie ▁Pres erve ▁in ▁Oklahoma ▁which ▁is ▁owned ▁by ▁the ▁Nature ▁Conserv ancy . ▁Ted ▁Turner ▁is ▁the ▁largest ▁private ▁owner ▁of ▁b ison ▁with ▁about ▁ 5 0 , 0 0 0 ▁on ▁several ▁different ▁ran ches . ▁ ▁The ▁current ▁American ▁b ison ▁population ▁has ▁been ▁growing ▁rapidly , ▁and ▁is ▁estimated ▁at ▁ 3 5 0 , 0 0 0 ▁compared ▁to ▁an ▁estimated ▁ 6 0 ▁to ▁ 1 0 0 ▁million ▁in ▁the ▁mid - 1 9 th ▁century . ▁Most ▁current ▁her ds , ▁however ▁are ▁gen et ically ▁poll uted ▁or ▁partly ▁cross bre d ▁with ▁cattle