In 1803, President Jefferson, acting for the United States, bought of France, through Napoleon, all the country west of the Mississippi, which LaSalle had claimed and named Louisiana. That vast region was sold for fifteen million dollars, which amounted to only two and a half cents an acre. This act is known as the Louisiana Purchase. The new country, called Louisiana Territory, was an unknown region thousands of miles in extent. Traders had gone up the Missouri River a few hundred miles, and voyagers along the Pacific coast had traded with the Indians at the mouth of the Columbia River; but no one knew much about the wide expanse of territory lying between, or of the rise and course of either of those great rivers. So it was decided that some one should undertake the long and dangerous journey among savage tribes and wild beasts, [Illustration: LEWIS AND CLARK ON THEIR EXPEDITION INTO THE FAR WEST. _From an old painting_] and find out all about the region. Young Lewis had wished years before to explore that country and had been kept from going, so now he begged the President to let him take charge of the great hunt for facts. The President had good reasons for consenting. He knew that Captain Lewis was brave, firm, and persevering, and that nothing could turn him from his purpose. He was well acquainted with the character and customs of the Indians, and was used to the hunting life. He had carefully studied the plants and animals of his own country. Above all, he was honest, fair-minded, and truthful, so that whatever he might report would be sure to be true. For these reasons the President felt no hesitation in trusting Captain Lewis to do so important a task. With fatherly pride ex-President Jefferson afterward wrote that young Lewis was not certain that he could do this great work right; so he attended a scientific school to learn more about plants, animals, minerals, physical geography and astronomy. He wanted all he should see to be of the highest value to his own country and to the other nations which claimed the great tracts next to the vast territory he had been appointed to explore. Besides, he went to a factory where firearms were made, so as to gain the working knowledge he might need some time to save the lives of his party. He started down the Ohio by boat from Pittsburgh. At Louisville he picked up his former neighbor, William Clark, brother of George Rogers Clark. He had been a mighty hunter and Indian fighter, and had served his country under General Anthony Wayne. Captain Lewis thought it best that there should be two leaders, in case of any accident to himself. The two captains were real comrades and generous commanders, keeping the respect and friendship of their men through the many hardships of their wanderings in the wilderness.