The short-lived stability in Europe was the background for the second great continental expansion gained by the American Republic. Napoleon, seeking new worlds to conquer, looked to North America and considered an economic empire on the British model, based on trade: Caribbean sugar to Europe, French manufactured goods to French settlers in temperate Louisiana, and temperate climate foodstuffs to the Caribbean to feed the slave labor there. It was at best a risky scheme, for a slave revolt had been raging in Santo Domingo, the principal French sugar island; Americans were pressing across the eastern Mississippi Valley; and French factories were not yet prepared to supply colonial demands. Most important, the French navy was too weak to defend this ambitious trade against the jealous British. Nevertheless, Napoleon persuaded Spain to exchange Louisiana for the Italian province of Tuscany (intended for the king of Spain's brother-in-law) and prepared an army for Santo Domingo.
When the new American president, Thomas Jefferson, learned about the secret retrocession of Louisiana, he instructed the U.S. minister to France, Robert Livingston, that he must bring Napoleon to sell the city of New Orleans to the United States. "[From] the day that France takes possession of New Orleans," Jefferson declared, "we must marry ourselves to the British fleet and nation." Livingston spent most of 1802 trying to convince Napoleon of the worthlessness of Louisiana without the Florida coast (which Spain refused to give up) and the near-certainty of friction with the United States. After several months of this deadlock, the Spanish government, which, with characteristic delay, had not yet carried out the retrocession, withdrew the right of deposit in New Orleans—for reasons about which historians are still uncertain. The American westerners, seeing their flourishing New Orleans trade thus abruptly cut off, flared up in protest, calling for action, and the Federalist Party, now out of power, began to demand a renewal of the war with France and the seizure of New Orleans. To gain time, Jefferson sent James Monroe, a well-known Virginian who was popular both in the west and in France, to join Livingston. During the three months between Monroe's appointment and his arrival in Paris, Napoleon impulsively decided to sell to the Americans not only New Orleans but the entire province of Louisiana, comprising the western half of the Mississippi Valley. As reconstructed by historians, the reasons for this momentous decision constitute one of the classic historic cases of multiple causation. In the first place, Napoleon's plan for an economic-based empire was falling apart. The conquest of Santo Domingo, the hub of the project, was going badly; yellow fever had decimated the French troops, and in November General Leclerc died of the disease. Napoleon had to send his successor troops that he had intended for the takeover of Louisiana from the Spanish. Those that remained were held in a Dutch port by an unusually hard winter. From his minister in the United States, Napoleon was learning of the American upheaval over the right of deposit, more serous than he had first thought. Finally, and perhaps decisive, tension in Britain and on the Continent suggested that the stalled war was about to break out again. Napoleon was beginning to turn his attention to possible hostilities in Europe, for which he would need funds.
Monroe and Livingston negotiated the terms of the purchase together, although each later tried to claim principal credit for the deal. The French asked 100 million francs at first but settled for 60 million ($11,350,000). The Americans, not having cash, arranged to pay in bonds at 6 percent. In addition, the United States assumed $3,750,000 of French citizens' claims, making the total purchase price about $15 million. The negotiations were hurried through in less than a month to fore-stall the outbreak of war or any interruption by Britain or Spain. The boundary of Louisiana was loosely drawn, but it clearly did not include East or West Florida or Texas, as some Americans later argued. Jefferson welcomed the news (which he had partly anticipated), although he was embarrassed by the doubtful constitutionality of the act. At first, he thought a constitutional amendment would be required, but he quickly dropped this scruple for fear that the providential deal might fall through at the last minute. Most of the Federalists held their peace too after a little grumbling.
The aftermath of the Louisiana Purchase was an anticlimax that took some of the bloom off Jefferson's successful first administration. After the negotiations were over, both Livingston and Monroe decided that the Louisiana Purchase included East and West Florida (that is, the peninsula and the Gulf coast to the Mississippi). On Jefferson's instructions, they put pressure on both Napoleon and the Spanish government with no success. Unwilling to go to war, Jefferson reconciled himself to a waiting game and got Congress to set up Mobile Bay as a customs district and later to appropriate $2 million to have on hand in case of an unexpected opportunity. The sorriest development of the whole period was the Burr Conspiracy (1804–1806), in which Aaron Burr, an outcast after his duel with Alexander Hamilton, exploited western unrest to concoct what was either a secessionist intrigue or a filibuster plot aimed at Texas and Mexico.
Madison, less patient than Jefferson, resorted to covert force and guile. When the inhabitants of the Baton Rouge area grew restive under Spanish rule, he sent an agent to tell them that the United States would welcome a revolution and warned off the British, whereupon the inhabitants seized the feeble Spanish fort. The rest of West Florida and part of East Florida fell to George Mathews, a revolutionary war veteran who led a force of "patriots" across the border. When Madison's opponents attacked the illegality of the act, he repudiated his agent, much to Mathews's disgust.
Following the War of 1812, the Monroe administration reverted to diplomacy to complete the acquisition of Florida. But force and the threat of force were not wholly absent from the process. After peace returned, General Andrew Jackson, commander of the military district on the southern border, broadly interpreted his vague orders and led troops into East Florida to fight Indians and protect border settlers. In the process, he captured several Spanish forts and executed two British army officers who, he said, were inciting the Indians against the Americans. Spain protested but realized that it might lose Florida anyway without action and agreed to treaty negotiations, especially after Secretary of State John Quincy Adams answered the protest with an aggressive reply, "a great gun from Washington to Madrid," as Adams's nephew pronounced it. (The British also protested but then dropped the matter.) The treaty was mainly devoted to the west boundary of the Louisiana Purchase, which was drawn on a zigzag line from the Sabine River on the modern Louisiana-Texas border to the modern north border of California (42 degrees). Many nationalists, especially southerners, resented the relinquishment of the slight American claim to Texas, but thereby the United States gained the equally weak Spanish claim to the Pacific coast, which helped to redirect American political power toward the West.
The War of 1812 gained no new territory for the United States, but it was important for avoiding the loss of land to the north and northwest. The United States went to war proclaiming, "On to Canada!" and hoping to acquire the Ontario peninsula at last. The British, for their part, hoped to set up an Indian protectorate between the Great Lakes and the Ohio River, both to halt the American westward movement and to create trade. They also planned sizable boundary adjustments in New England, New York, and the Northwest. By 1814 the ambitions had shrunk so far that the negotiations produced a status quo ante peace. This was quite enough for the Americans, who received it with relief as a renewed guaranty of their independence.
Two postwar agreements, each having the effect of a treaty, refined and strengthened the original treaty of 1783 fixing the northern boundary of the United States. The Rush-Bagot Agreement of 1817 limited naval armament on the Great Lakes. The Convention of 1818 drew the northern boundary along the parallel of 49 degrees from the Lake of the Woods to the "stony mountains" and provided that the territory from the mountains to the Pacific coast should be occupied by British and Americans without injury to claims of either country (generally called "joint occupation"). The convention was to last ten years, renewable until denounced. It also ended two vestiges of the past, the "boundary gap" of 1783 and the much-argued British right of navigation on the Mississippi.
A large boundary gap had existed since 1783 at the eastern end of the north border, from the point where the forty-fifth parallel crosses the St. Lawrence River to that where the St. Croix River enters the Bay of Fundy (comprising the modern north borders of New York, Vermont, New Hampshire, and Maine). Local inhabitants disagreed as to which of several rivers was "the true St. Croix." Afterward, a trail of boundary commissions, documents, and maps led from the Peace of Paris to the Treaty of Ghent without any definition of "the North West Angle of Nova Scotia," the "north-western-most head" of the Connecticut River, and other place names on the outdated Mitchell map of 1755. The War of 1812 gave new importance to the boundary controversy, for it convinced the British that they needed a military road between Quebec and Halifax.
The admission to the union of the state of Maine in 1820 also complicated the question, because Massachusetts still had land claims in the disputed area, so now there were two sets of governors, legislatures, newspapers, and citizenry squabbling over geographical details, to say nothing of the federal government in the national system. Two efforts after 1815 to settle the question added further problems, because a boundary commission discovered that an expensive American fort at Rouse's Point had been built on Canadian soil through a surveying error. Also, a boundary line drawn by an arbiter, the king of the Netherlands, did not satisfy many Americans, who accused him of pro-British bias. The nationalist Andrew Jackson, however, thought the dispute had gone on long enough and tried in vain to get the king's award accepted.
It took a major Anglo-American crisis to bring about a solution to the Maine boundary problem. In 1837 a double revolution for self-government in Ontario and Quebec drew in hotheaded sympathizers and covetous expansionists from upper New York State, eager to strike a blow for freedom and mount a filibuster at the same time. A land war broke out in northern Maine when frontiersmen from both sides of the line discovered the Aroostook Valley, a pocket of fertile land, and started to fight over it. The commanding general of the American army, Winfield Scott, was sent to intervene and restore peace, and Britain appointed a diplomat, Lord Ashburton, to negotiate a settlement. He and Secretary of State Daniel Webster (who happened to be his personal friend) managed to draw a compromise line with information from sixty-year-old maps. By a curious anomaly, each side possessed information supporting the other side's case. Webster showed his maps to the Maine politicians to silence their objections; whether he also used money supplied by Ashburton has fascinated and baffled everyone who has written on the subject. In any case, it seems likely that Webster's attentions made a peaceful outcome possible but lost the United States about five thousand square miles of Maine woods and swamps. Smaller adjustments were made to the west in New Hampshire and Vermont, and the United States gained a sliver of land in New York, including "Fort Blunder" on Rouse's Point. More important was a cession of about six thousand square miles in Minnesota that proved later to contain some of that state's invaluable iron ore deposits.
The Monroe Doctrine, enunciated in the president's annual message of December 1823, did not contribute directly to continental expansion, for much of it applied to Central and South America. However, one part of it, the noncolonization principle, foreshadowed the annexation of Alaska forty-four years later. In 1821 the czar of Russia, seeking to expand his control over his far-away colony, issued a ukase claiming its boundary to 51 degrees north latitude and forbidding non-Russian ships to come within one hundred miles of this coast. When a burst of protest from New England farming and fishing interests followed, Secretary of State John Quincy Adams, their perennial champion, got Monroe to announce in his message that the Western Hemisphere was no longer open to European colonization. By implication Adams intended his warning for Britain as well as Russia. It had no basis for legality in international law, but the czar never enforced his ukase. In a treaty of 1824 Russia fixed the southern boundary of its colony at 54 degrees, 40 minutes—the "fifty-four forty" of a later American political slogan.