Captain William Clark and the Corps of Discovery camped on July 16, 1806, under the shade of cottonwood trees on the north side of the Yellowstone River. This valley provided grass for their 50 horses to graze and abundant wildlife, a blessing after periods of near starvation earlier in their journey. On July 17, 1806, Clark wrote, "Saw a large gangue of about 200 Elk and nearly as many Antilope...."