View northeast, above Sacrifice Cliff
At right, opposite the city (pop. 100,000) of Billings, Montana is the landmark William Clark identified on 24 July 1806 as "a high clift of yellowish Gritty Stone on the Stard Side." It is now known as Sacrifice Cliff. Six miles back up the Yellowstone from this rimrock, Clark had his detachment's 26 remaining horses driven across to the south side of the river, then ferried Sgt. Pryor, with Pvts. Shannon and Windsor, across in the dugout catamarans. Pryor's route took them south east (right) of the cliff and parallel to the river for the the next two days, when an unexpected event suddenly changed their plans.
While waiting for Pryor to catch up with the canoes on the twenty-fourth, Clark had observed what possibly was a Sun Dance lodge of the Crow Indians.
View northeast, down the Yellowstone
That night Clark and the rest of his party camped a little below a "bold" stream that was 35 yards wide, which he labeled "Pryers river." It entered the Yellowstone at the far edge of the refinery at upper right. It may have qualified as a river back then, but nowadays it is more suitably known as Dry Creek. Perhaps that is why the next morning, on second thought, some eight miles farther downstream—in the distance, about where the Yellowstone bends north for the second time in this view—he labeled another watercourse "Pryors Creek." Inexplicably, "Pryor's River" made the cut for Clark's final map, which accompanied Nicholas Biddle's 1814 paraphrase of his and Lewis's journals, while the longer, more substantial "Pryors Creek," which is still labeled with that name on modern maps, was overlooked.