President Jefferson sent Meriwether Lewis and William Clark to explore the Missouri River and find a stream from its headwaters to the Pacific that would provide the best water route for developing commerce. Lewis and Clark left on May 14, 1804, reached the mouth of the Osage on June 1, passed the mouth of the Nodaway on July 8 and the Nishnabotna on July 14, and began poling and sailing along the southwestern border of Iowa on July 18. On July 29 they encamped on Iowa soil a short distance above the mouth of the Boyer River, and the next day they put in on the Nebraska shore at a place they called Council Bluff to await the Missouri and Oto Indians. When the Indians arrived on August 3, Lewis and Clark told them of their mission up the Missouri, advised them on how they were to conduct themselves, and presented the chiefs with medals, a canister of powder, and a bottle of whiskey. Lewis and Clark traveled up the Missouri with 43 men and spent 33 days along the western border of Iowa. Sergeant Charles Floyd, the only man to die on the expedition, fell ill on August 19, 1804, died on August 20 on Iowa soil, and was buried near present-day Sioux City with the honors of war on a bluff one-half mile below a small river that was given his name. The monument erected in 1900-1901 in his honor was the first Registered Historic Landmark in the United States.