The bedrock in Portneuf Narrows is ancient volcanic rock of the Bannock Volcanic Member of the Pocatello Formation, and other distinctive rock in the area records a continent-scale glaciation about 700 million years ago. After the Fort Hall Indian Reservation was opened to settlement in 1902, a copper mine was established in Fort Hall Mine Canyon directly south. A railroad siding and bunkhouse served the area. A vein of chalcopyrite copper ore was mined for several years, but a cross-fault cut off the vein, and despite 400 feet of tunnel driven under the mountain, it was never found again.