The Louisiana Purchase doubled the size of the United States. Jefferson's principal interest was understanding the geography for water travel for the purposes of commerce. A huge part of the expedition was also meeting the various Indian tribes across the land and introducing them to the U.S. For the most part Lewis and Clark and their men were greeted a little warily but warmly, and these meetings are a fascinating part of their 4,000 mile journey and the westward expansion of the USA.
