In 1964, explorer parachutist Jean Poirel from Montreal jumped at its source north of Yellowknife, followed by his teammate Bertrand Bordet. Jean Poirel imagined the idea of going down the river with inflatable dinghies. During the following four consecutive expeditions in the valley Jean Poirel discovered more than 250 caverns. The most important contained 116 Dall sheep’s skeletons (carbon-14 dated to 2500 years BC); Jean Poirel named it "Valerie Cavern" after his daughter. He took topographic notes and drew detailed maps, paving the way for the park's creation. During his last expedition in 1972, he escorted Pierre Trudeau, who came in person to evaluate this superb and fascinating region.