What US President launched the Lewis and Clark expedition?

Thomas Jefferson had dreamed of exploring the West for at least 20 years before he even became President. In 1783 he had even asked William Clark's brother, George, to take on the challenge. The Louisiana Purchase would later alter the character of the planned expedition from an exploration of French territory to a first glimpse of lands that, in the view of many contemporaries, were essential to maintaining the agrarian, republican character of the nation.

The Louisiana Territory had been a land purchase transaction by the United States of America of 828,800 square miles of the French territory "Louisiane" in 1803. The U.S. paid 60 million francs ($11,250,000) plus cancellation of debts worth 18 million francs ($3,750,000), a total cost of $15,000,000 for the Louisiana Territory. After finally purchasing the Louisiana Territory, Jefferson asked Lewis to go on the journey. Jefferson then requested $2500 from Congress to pay for the costs of the trip.