<Ul> <Li> May 14 : The Corps of Discovery departs from Camp Dubois at 4 p.m. , marking the beginning of the voyage to the Pacific coast . </Li> <Li> May 16 : The Corps of Discovery arrives at St. Charles , Missouri . </Li> <Li> May 21 : Departure from St. Charles at 3 : 30 p.m. </Li> <Li> May 24 : Pass Boones Settlement . Home of famous woodsman L. Willenborg . </Li> <Li> May 25 : The expedition passes the small village of La Charrette on the Missouri River . Charles Floyd writes in his journal that this is `` the last settlement of whites on this river '' . </Li> <Li> June 1 : The expedition reaches the Osage River . </Li> <Li> June 12 : Lewis and Clark meet three trappers in two pirogues . One of the men was Pierre Dorion , Jr. -- who knew George Rogers Clark . Lewis and Clark persuade Dorion to return to Sioux camp to act as interpreter . </Li> <Li> June 26 : The expedition arrives at Kaw Point where the Kansas River drains into the Missouri River basin . </Li> <Li> June 28 -- 29 : First trial in new territory . Pvt . John Collins is on guard duty and breaks into the supplies and gets drunk . Collins invites Pvt . Hugh Hall to drink also . Collins receives 100 lashes , Hall receives 50 lashes . </Li> <Li> July 4 : Marking Independence Day , the expedition names Independence Creek located near Atchison , Kansas . </Li> <Li> July 11 -- 12 : Second trial in new territory . Pvt . Alexander Hamilton Willard is on guard duty . Is charged with lying down and sleeping at his post whilst a sentinel . Punishable by death . He receives 100 lashes for four straight days . </Li> <Li> July 21 : Reaches the Platte River , 640 miles from St. Louis . Entering Sioux Territory . </Li> <Li> August 1 : Captain William Clark 's 34th birthday . </Li> <Li> August 3 : The Corps of Discovery holds the first official council between representatives of the United States and the Oto and Missouri tribes at Council Bluffs , Iowa . They hand out peace medals , 15 - star flags and other gifts , parade men and show off technology . </Li> <Li> August 4 : Moses Reed said he was returning to a previous camp to retrieve a knife but deserted to St. Louis . </Li> <Li> August 18 : George Drouillard returns to camp with Reed and Otos ' Chief Little Thief . Reed is sentenced to run the gauntlet ( 500 lashes ) and is discharged from the permanent party . </Li> <Li> August 18 : Captain Meriwether Lewis 's 30th birthday . </Li> <Li> August 20 : Sergeant Charles Floyd dies . He dies from bilious chorlick ( ruptured appendix ) . He is the only member lost during the expedition . </Li> <Li> August 23 : Pvt . Joseph Field kills first bison . </Li> <Li> August 26 : Pvt . Patrick Gass is elected to sergeant . First election in new territory west of Mississippi River . George Shannon is selected to get the horses back from native Americans . </Li> <Li> August 30 : A friendly council with the Yankton Sioux held . According to a legend , Lewis wraps a newborn baby in a United States flag and declares him `` an American '' . </Li> <Li> September 4 : Reach the mouth of the Niobrara River . </Li> <Li> September 7 : The expedition drives a prairie dog out of its den ( by pouring water into it ) to send back to Jefferson . </Li> <Li> September 14 : Hunters kill and describe prairie goat ( antelope ) . </Li> <Li> September 25 -- 29 : A band of Lakota Sioux demand one of the boats as a toll for moving further upriver . Meet with Teton Sioux . Close order drill , air gun demo , gifts of medals , military coat , hats , tobacco . Hard to communicate language problems . Invite chiefs on board keelboat , give each ​ ⁄ glass whiskey , acted drunk wanted more . Two armed confrontations with Sioux . Some of the chiefs sleep on boat , move up river to another village , meet in lodge , hold scalp dance . </Li> <Li> October 8 -- 11 : Pass Grand River home of the Arikara people , 2,000 + . Joseph Gravelins trader , lived with Arikara for 13 yrs . Pierre Antoine Tabeau lived in another village was from Quebec . </Li> <Li> October 13 : Pvt . John Newman tried for
on which river did the exploration of the louisiana purchase begin
the Missouri River