Powder River was a river which was possibly in, or near to, The Wasteland. It was destined to be the rendezvous point for Pappagallo's tribe after their flight from the Oil Refinery. According to Pappagallo the river supposedly had a large bridge that crossed it. The river was approximately 200 miles north of the oil refinery's compound.
It is likely that the compound dwellers reached Powder River and regrouped, for the Feral Kid lived on not only to tell Max's tale but also to become the Chief of the Great Northern Tribe.