William Clark was born on August 1, 1770 on his family's Virginia plantation. At age 14, Clark moved from Virginia to Louisville, Kentucky. Five years later, in 1789, Clark joined the militia to help fight the Native Americans in the Ohio Valley. After becoming an officer in the U.S. Army, Clark retired from service and went back to Virginia to manage his family's estate.

In 1803, Clark's life would change. After Thomas Jefferson's Louisiana Purchase, in which America acquired thousands of miles of land west of the Mississippi River, Meriwether Lewis, one of Clark's army comrades invited him to collaborate on a expedition across the new land. Their mission was not only to explore the new land, establish friendly relations with Indians and to discover new animals and plants, but to find the elusive Northwest Passage. Clark agreed and was made responsible for the expedition's records and map making.

Along with Meriwether Lewis, William Clark spent over two years exploring the new frontier. After successfully establishing Fort Clatsop, Oregon, and after discovering over 300 news species of animals and plants, the pair returned. Clark was appointed principal Indian agent and Brigadier General of the Louisiana Militia by Thomas Jefferson. After the deaths of Meriwether Lewis and Sacagawea, Clark adopted her children and became governor of the Missouri Territory in 1813. After an unsuccessful bid for governor of Missouri, Clark was made Superintendent of Indian Affairs in 1822. He held that position until his death on September 1, 1838.