Explorer, he was the only member of the Lewis and Clark Expedition to die during the expedition, and was the first United States soldier to die west of the Mississippi River. Floyd was born in Kentucky, and among the first to volunteer for service in the Corps of Discovery, as the Lewis and Clark expedition members called themselves. He was a cousin of the expedition's Sergeant Nathaniel Pryor, and was considered a "man of much merit" by Captain Clark, the expedition's leader. Sergeant Floyd was the expedition's quartermaster, and kept a daily record from which historians have used extensively. Floyd's diary shows that he judged land quality, soil conditions and other aspects of the land during the expedition. Floyd took ill on the evening of August 19, 1804, and died the next day at the age of 22, from what the expedition's leaders diagnosed as "bilious cholic." Medical historians have concluded that he really died from a ruptured appendix and its resulting peritonitis, judging from the classic symptoms that he displayed. Even if his medical condition had been correctly diagnosed, his condition was fatal and the best medical doctors of the day could not have saved him. Captain Clark recorded in his journal on August 20, 1804, "Sergeant Floyd much weaker and no better...no pulse and nothing will stay a moment in his stomach or bowels....Floyd died with a great deal of composure, before his death he said to me, 'I am going away. I want you to write me a letter.' We buried him on the top of the bluff. Half mile below is a small river to which we gave his name. He was buried with the Honors of War much lamented, a cedar post with the name 'Sergt. C. Floyd died here 20th of August 1804' was fixed at the head of his grave." Today, Floyd's grave is within the city limits of Sioux City, Iowa. Two years later, the expedition returned from reaching the Pacific Ocean, and found that animals had disturbed the grave. They restored the grave and replaced the fallen cedar marker of their comrade. In the years that followed, Floyd's bluff became a landmark for travelers going through the area. In 1857, the local citizens of Sioux City discovered that the Missouri River had eroded much of the grave, including the original cedar marker. The citizens restored both the grave and the marker, moving the grave back a further 600 feet from the river. His grave is now marked with a 100 foot obelisk of white sandstone, dedicated on May 30, 1901. In 1960, the grave and the land around it was made the first National Historic Landmark, and is part of a 23 acre park.