Louisiana and Britain
One of Jefferson's acts doubled the area of the country. At the end of the Seven Years' War, France had ceded its territory west of the Mississippi River to Spain. Access to the port of New Orleans near its mouth was vital for the shipment of American products from the Ohio and Mississippi river valleys. Shortly after Jefferson became president, Napoleon forced a weak Spanish government to cede this great tract, the Louisiana Territory, back to France. The move filled Americans with apprehension and indignation. French plans for a huge colonial empire just west of the United States seriously threatened the future development of the United States. Jefferson asserted that if France took possession of Louisiana, "from that moment we must marry ourselves to the British fleet and nation."
Napoleon, however, lost interest after the French were expelled from Haiti by a slave revolt. Knowing that another war with Great Britain was impending, he resolved to fill his treasury and put Louisiana beyond the reach of Britain by selling it to the United States. His offer presented Jefferson with a dilemma: The Constitution conferred no explicit power to purchase territory. At first the president wanted to propose an amendment, but delay might lead Napoleon to change his mind. Advised that the power to purchase territory was inherent in the power to make treaties, Jefferson relented, saying that "the good sense of our country will correct the evil of loose construction when it shall produce ill effects."
The United States obtained the "Louisiana Purchase" for $15 million in 1803. It contained more than 2,600,000 square kilometers as well as the port of New Orleans. The nation had gained a sweep of rich plains, mountains, forests, and river systems that within 80 years would become its heartland -- and a breadbasket for the world.
As Jefferson began his second term in 1805, he declared American neutrality in the struggle between Great Britain and France. Although both sides sought to restrict neutral shipping to the other, British control of the seas made its interdiction and seizure much more serious than any actions by Napoleonic France. British naval commanders routinely searched American ships, seized vessels and cargoes, and took off sailors believed to be British subjects. They also frequently impressed American seamen into their service.
When Jefferson issued a proclamation ordering British warships to leave U.S. territorial waters, the British reacted by impressing more sailors. Jefferson then decided to rely on economic pressure; in December 1807 Congress passed the Embargo Act, forbidding all foreign commerce. Ironically, the law required strong police authority that vastly increased the powers of the national government. Economically, it was disastrous. In a single year American exports fell to one-fifth of their former volume. Shipping interests were almost ruined by the measure; discontent rose in New England and New York. Agricultural interests suffered heavily also. Prices dropped drastically when the Southern and Western farmers could not export their surplus grain, cotton, meat, and tobacco.
The embargo failed to starve Great Britain into a change of policy. As the grumbling at home increased, Jefferson turned to a milder measure, which partially conciliated domestic shipping interests. In early 1809 he signed the Non-Intercourse Act permitting commerce with all countries except Britain or France and their dependencies.
James Madison succeeded Jefferson as president in 1809. Relations with Great Britain grew worse, and the two countries moved rapidly toward war. The president laid before Congress a detailed report, showing several thousand instances in which the British had impressed American citizens. In addition, northwestern settlers had suffered from attacks by Indians whom they believed had been incited by British agents in Canada. In turn, many Americans favored conquest of Canada and the elimination of British influence in North America, as well as vengeance for impressment and commercial repression. By 1812, war fervor was dominant. On June 18, the United States declared war on Britain.