By the end of the eighteenth century, the country between the Alleghanies and the Mississippi was fairly well known, first through the explorations of such pioneers as Boone and Clark and Kenton, and, later on, through the steady advance of civilization, forever throwing new outposts westward. But beyond the great river stretched a mighty wilderness whose character and extent were only guessed at. The United States, of course, had little interest in it, since it belonged to France, and since, east of the river, there were millions of acres as yet unsettled; but when, in 1803, President Jefferson purchased it of Napoleon Bonaparte for the sum of fifteen million dollars, all that was changed. By that purchase, the area of the United States was more than doubled; but there were many people at the time who opposed the purchase on the ground that the country east of the river would never be thoroughly settled and that there would be no use whatever for the great territory west of it. So mistaken, sometimes, is human foresight! The President determined that this great addition to the Nation should be explored without delay, and, securing from Congress the necessary powers, he appointed his private secretary, Captain Meriwether Lewis, to head an expedition to the Pacific. Lewis was at that time twenty-nine years of age. He seems to have been of an adventurous disposition for, despite the fact that he inherited a fortune, he enlisted in the army as a private as soon as he was of age. Five years later, he had risen to the rank of captain, and, attracting the attention of President Jefferson, he was appointed his secretary. He proved to be so capable and enterprising that the President selected him for this dangerous and arduous task of exploration. With him was associated Lieutenant William Clark, a brother of that hardy adventurer, George Rogers Clark. William Clark, who was eighteen years younger than his famous brother, had joined him in Kentucky in 1784, at the age of fourteen, and soon became acquainted with the perils of Indian warfare. He was appointed ensign in the army four years later, and rose to the rank of adjutant, but was compelled to resign, from the service in 1796, on account of ill-health. He settled at the half-Spanish town of St. Louis, and in March, 1804, was appointed by President Jefferson a second lieutenant of artillery, with orders to join Captain Lewis in his journey to the Pacific. Clark was really the military director of the expedition, and his knowledge of Indian life and character had much to do with its success.