" In other words, republicanism in an expanding state would inevitably lead to more despotic, aristocratic, and monarchical regimes. Hence, if the U.S. were to follow a policy of expansion, it would, at least, theoretically conflict with its republican origins.
Interestingly, one of the leading proponents of republicanism, Thomas Jefferson had become the third U.S. President after an unexpected electoral crisis in the elections of 1800. He was a great champion of the rights of the individuals and the states rather than a strong central government. At the same time, the international political situation at the time -- with several European powers vying to consolidate their colonial presence in the Americas -- dictated an opposite direction for the U.S. foreign policy to safe-guard its national interests, i.e., a policy of Westward Expansion and the fulfillment of the Manifest Destiny to make the U.S. A dominant power in North America. The way in which Jefferson dealt with the dilemma, determined to a large extent the future course of American history in the west.
The huge territory of Louisiana, covering almost 800,000 square miles, stretching from the Canadian border to the mouth of the Mississippi, and from the western bank of the river to the Rockies, was the key to future power play in the region. It had been nominally under Spanish control at the time of United States' independence but Spain was a declining colonial power in the 18th century and France, under Napoleon Bonaparte, was now displaying ambitions for re-establishing its colonial empire in North America, which it had lost in the Seven Years' War (1754-1761) with England and her continental allies. The first step in the French plan was its desire to re-conquer the island of Santa Domingo Island (present day Haiti and Dominican Republic) which had been lost due to a civil war and the emergence of its black leader, Toussaint L'Ouverture, who had taken control and declared independence. The main obstacle to the French plans was the opposition of the U.S. government towards such a move by France in its backyard. When Jefferson -- a known friend of the French -- became the U.S. President, he reversed the hostile U.S. policy towards France and gave his tacit consent to a French invasion to retake the Santa Domingo island.
Buoyed by the change in the American policy, Napoleon set in motion his more ambitious plans for colonial expansion in North America. He signed a treaty of friendship with the U.S. while secretly making a secret deal with Spain for returning the territory of Louisiana, which France had earlier given to Spain in 1763 as compensation for its losses as an ally in the Seven-Year War with England. Jefferson, who until then had trusted the French, was shocked when he learnt of the secret Franco-Spanish deal over Louisiana. French control of the Mississippi river system and the important port city of New Orleans was simply unacceptable to the U.S.; it would have exposed the still shaky Union to a powerful neighbor in the west with the ability to de-stabilize its southern states by fermenting trouble among their large slave populations. It would also have undermined its economic well-being by controlling the important trade outlet of the Mississippi Valley at New Orleans. The U.S. Federalists who were already hostile to France, pressed the government for a pre-emptive strike on New Orleans before the French could take physical control of the city. Jefferson, however, was aware of the weakness of his country's military and the problems it would have to face by entering into a war with France at that stage. In desperation, he sent Robert R. Livingston as his ambassador to France to convince them to sell New Orleans and the Floridas to the United States. Left with few cards to play with, Jefferson let it be known to the French that he was prepared to enter into a military alliance with Britain against France if the latter did not play ball.
Just when it seemed unlikely that the French would agree to such a proposal, providence intervened in the shape of unexpectedly stiff resistance by the rebels to the invading French forces in Santa Domingo. With the help of 'extraneous' factors such as a raging yellow fever epidemic and other devastating tropical diseases among the French, the rebels fought a French expeditionary force of more than 20,000 to a standstill. Napoleon was now faced with the choice of committing much larger forces to the island and the American mainland or to abandon his imperialistic ambitions in the west. Faced with the imminent resumption of war in Europe with his arch-enemy -- the British, Napoleon decided to cut his losses. In April 1803, his representative offered the entire Louisiana Territory to the surprised American negotiators who were at best hoping to persuade the French to sell just New Orleans and the Floridas. What is more, the French were willing to sell the entire 828,000 square miles of territory for just $15 million (with $5 million included for U.S. claims on the French). The price was dirt cheap and far below the U.S. expectations as, unknown to the French, the American negotiators had been authorized to pay $10 million for just New Orleans and the Floridas.
The Louisiana Purchase was a momentous event in the country's history: it more than doubled the existing territory of the United States; opened the mid-west to white American settlers, and most of all, guaranteed the survival of the Union at a crucial stage by eliminating the danger of a powerful French presence at the mouth of the Mississippi.
Moving Further West
The successful acquisition of such vast territories through the Louisiana Purchase only whetted the appetite of the Americans to extend their borders further west right down to the Pacific. The U.S. government had gathered useful information about the western territory through the Lewis and Clark Expedition (1804-06) and the reports had been encouraging. There were three major areas in the west on which the Americans set their eyes to complete their dream of an 'ocean to ocean' nation: Texas to the south and south-west of the newly acquired Louisiana, which was part of Mexico; Oregon country (consisting of the present-day Washington, Oregon, and Idaho states) that was claimed by the British; and territory up to the Pacific coast west of Louisiana including California, Nevada, Utah, and Arizona that was still under the control of Mexico.
The Texas Annexation: The Louisiana Purchase led to a border dispute between the U.S. And Spain over Texas. The U.S. insisted that the purchase included land to the east of Rocky Mountains and to the north of Rio Grande; Spain disputed the validity of the Louisiana Purchase since France had categorically agreed not to sell the territory to a third party while acquiring it from Spain. The dispute was settled to an extent by the Adams-Onis Treaty in 1819 in which Sabine River was recognized as Texas's eastern boundary. Texas, however, did not remain under Spanish control for long and became a part of Mexico in 1821 at the end of the Mexican War of Independence against Spain. It also signaled the end of a Spanish law that only settlers of full-blooded Spanish descent could settle in Texas. Anglo-American families started to settle in Texas and by 1830 their number had grown to 30,000 -- far outnumbering the Tejanos (settlers of Latin-American descent). The new settlers resented the ham-handed central rule from Mexico City and were apprehensive that slavery may soon be abolished in the state by the Mexican government since their economy depended on slave labor to a large extent; they proceded to declare the independence of Texas in 1836 making it the Republic of Texas. Most Anglo-American settlers wanted to join the United States but its absorption into the Union was opposed by the Northern states as it would increase the number of slave-owning states. However, when James Polk won the 1944 U.S. President on a Texas-annexation platform, the U.S. Congress promptly passed a resolution for annexing Texas, making it a part of the Union. Mexico had never recognized the independence of Texas and had warned that its annexation by the U.S. would mean war. War with Mexico was more than welcome for the Polk administration since it afforded the U.S. its long-held opportunity of gaining access to the Pacific by acquiring more Mexican territory in the West, i.e., the territories of present day California, Nevada, New Mexico, Utah and Arizona.
The Mexican-American War: Even as Mexico delayed its declaration of war in the aftermath of the U.S. annexation of Texas, the Polk administration further pushed it against the wall by claiming that the southern border of Texas lay at the River Rio Grande rather than at the…