The annual John Colter Day celebration will be held Monday, June 29, at Colter Bay Visitor Center in Grand Teton National Park. Colter explored the vast Yellowstone country during the winter of 1807-08, and was likely the first European-American to travel the region. This marks the eighth year that Grand Teton has offered special presentations to highlight the life of John Colter and the mountain men of the 1800s.