Why did the United States follow a policy of expansionism in the late 1800s?

The history of Hispanic representation in Congress is entwined with that of U.S. continental expansion in the 19th century.7 In the decades of rapid westward advance and settlement between the signing of the Adams-Onís Treaty of 1819 and the declaration of the Spanish-American War in 1898, the House nearly doubled in size.8

Thomas Jefferson, James Madison, and Westward Expansion

/tiles/non-collection/p/part1_04_madison_james_hc.xml Collection of the U.S. House of Representatives
About this object Considered the Father of the United States Constitution, James Madison of Virginia served four terms in the House (1789–1797). Like Thomas Jefferson, Madison saw the strategic value of securing the United States from foreign encroachment by acquiring East and West Florida.

President Thomas Jefferson spearheaded westward expansion when the United States acquired the Louisiana territory from France in 1803 and sponsored Lewis and Clark’s expedition (1805–1807). Jefferson’s foreign policy goal to expand U.S. territory westward was intended to help the U.S. have greater freedom in dealing with foreign powers on the North American continent and to consolidate the power of the young republic. It required developing military strength and practicing shrewd diplomacy.9 The policies Jefferson implemented, particularly regarding U.S. expansion in the modern Gulf Coast region, persisted through two more presidential administrations.

After securing the Louisiana territory, Jefferson and his successors focused on acquiring Spanish Florida—which encompassed all of modern-day Florida, as well as a strip running along the Gulf Coast to the Mississippi River. New possibilities for commerce and ports along the Gulf Coast were one rationale. National security was another: Florida offered strategic value in securing Louisiana, the Mississippi Territory, and Georgia. President James Madison employed his predecessor’s tactics. In West Florida—which extended from Baton Rouge, on the east bank of the Mississippi River in modern-day Louisiana, to Pensacola, in the panhandle of modern-day Florida—U.S. settlers became the majority population from 1805 to 1810. The settlers resisted weakened Spanish rule and advocated for American sovereignty. In 1804 Congress passed the Mobile Act, which extended U.S. federal revenue laws to all territories ceded by France, including West Florida. The act also granted the President “discretionary authority” to take possession of the Mobile area.10 In 1811 Madison asserted U.S. jurisdiction over the area and had incorporated West Florida into Louisiana. The United States annexed Mobile during the War of 1812.

Adams-Onís Treaty (Transcontinental Treaty)

Spain claimed the lands that constitute present-day Florida in addition to the land stretching from its panhandle westward, across the southern portions of modern-day Alabama and Mississippi to the eastern banks of the Mississippi River. General Andrew Jackson’s invasion of Florida during the First Seminole War (1817–1818) spurred the Spanish government—fearing the loss of its claim to the territory—to the negotiating table. Benefiting from favorable geopolitical circumstances, Secretary of State John Quincy Adams entered into negotiations with Spanish diplomat Don Luis de Onís in 1819. In return for the United States’ renouncing its tenuous claims to Texas and paying $5 million for U.S. citizens’ claims against Spain, Adams secured all of Spanish Florida, finalizing the Louisiana Purchase. The treaty also set a new boundary running from the mouth of the Sabine River on the Gulf Coast (on the eastern border of modern-day Texas) northwestward along portions of the Sabine, Red, and Arkansas Rivers, then westward on the 42nd parallel to the Oregon coast. It was the first boundary to traverse the U.S. continent.

/tiles/non-collection/p/part1_05_adams_john_quincy_hc.xml Collection of the U.S. House of Representatives
About this object Secretary of State John Quincy Adams of Massachusetts, the lead negotiator of the Adams-Onís Treaty, enjoyed a prominent political career as a foreign minister, U.S. Senator, and President before serving in the U.S. House of Representatives for nine terms (1831–1848).

The Adams-Onís Treaty also ushered in Congress’s first Member of Hispanic descent; Joseph Marion Hernández served as Florida’s first Territorial Delegate during the 17th Congress (1821–1823).11 Pursuing an agenda that was typical for a Territorial Delegate, Hernández sought to secure infrastructure improvements that would benefit economic growth and bolster political arguments for Florida’s admission into the Union as a state. A wealthy planter and military figure who had fought for Spanish interests in the Patriot War and the First Seminole War, Hernández helped bridge the transition from Spanish rule to American governance. It would be 30 years after Hernández’s departure from the House in March 1823 until the next Hispanic Member arrived in Congress. Like many Territorial Delegates in the 19th century, Hernández returned home to a prominent career in local politics and business; he served in the legislature and led a militia in the Second Seminole War in the 1830s before making an unsuccessful bid for a U.S. Senate seat when Florida became a state in 1845.

Though the Adams-Onís agreement resolved one friction point, it created others. Critics charged that President James Monroe and Secretary of State Adams yielded legitimate claims to Texas, fueling later demands for Texas’ “re-annexation,” particularly by pro-slavery advocates in the 1830s. Moreover, the Adams-Onís Treaty validated Mexican ownership of lands that would become targets for U.S. expansion during the War with Mexico from 1846 to 1848.

Manifest Destiny

/tiles/non-collection/p/part1_06_manifest_destiny_drawing_lc.xml Image courtesy of the Library of Congress Titled American Progress. Westward the course of destiny. Westward ho!, this print memorializes the movement of U.S. settlers across the continental United States during the 1840s and 1850s.

Powerfully articulated in the Monroe Doctrine of 1823, Adams’s coolheaded geopolitical calculations provided later generations of U.S. officials with a road map for the advancement of American dominion in the Western Hemisphere. Meanwhile, Americans in the 1830s and 1840s justified their march across the continent under the rubric of “Manifest Destiny.” Coined by a New York newspaper, the term described the popular desire for geographic expansion and, as such, was more a zeitgeist than an official foreign policy strategy in antebellum America.12 Though derived from complex circumstances, Manifest Destiny was amenable to different political agendas and worldviews, and thus its appeal cut across regional, party, and class lines.13 At the laying of the cornerstone of the Washington Monument on July 4, 1848, Speaker of the House Robert Winthrop captured the mood, employing a metaphor that evoked the era’s ultimate symbol of progress: “The great American built locomotive ‘Liberty’ still holds it course, unimpeded and unimpaired; gathering strength as it goes,” he said. “Nor can we fail to observe that men are everywhere beginning to examine the model of this mighty engine, and that not a few have already begun to copy its construction and to imitate its machinery.… The whole civilized world resounds with American opinions and American principles,” he added. “Every vale is vocal with them. Every mountain has found a tongue for them.”14

In the eyes of many observers there was little difference between federal policy and popular will. It was America’s obligation, one pundit wrote in 1845, “to overspread and to possess the whole continent which providence has given us for the development of the great experiment of liberty and federated self government.”15 Such seemingly inevitable growth justified America’s rapid acquisition of Western lands and amplified the nationalist sentiments of U.S. settlers in Texas and the Pacific Northwest in the 1840s.16

However, the concept of expansion veiled multiple motives and was advocated by Northerners and Southerners for different reasons. While many Americans supported it, such growth awakened sectional debates over slavery. The possibility of new Western lands forced the federal government to confront questions that had been somewhat mollified since the Missouri Compromise of 1820: Would new states allow slavery or oppose it? How would Congress maintain its balance of sectional interests? Expansionists, moreover, did not address the potential effects of rapid development on African Americans, American Indians, and Mexican citizens living in contested territories.17

Texas Revolution and Annexation

The boundaries that were ratified in the Adams-Onís Treaty, yielding Texas to New Spain, were swiftly altered in 1821 when Mexico replaced Spain as the sovereign, and U.S. settlers quickly began to cross into East Texas.18 Throughout the 1820s, Anglos streamed into the Mexican province, outnumbering Hispanic Texans by two to one within a decade. The Mexican government sought to prohibit the slave trade, and in 1830 the Mexican Congress passed a law that suspended U.S. immigration into Texas.

/tiles/non-collection/p/part1_07_santa_anna_lc.xml Image courtesy of the Library of Congress In this political cartoon, Texas Army Commander-in-Chief Sam Houston (left) accepts the surrender of General Antonio López de Santa Anna. After achieving independence, Texas existed as an independent republic until its admission as a U.S. state in 1845.

In 1834, the year after he assumed power, General Antonio López de Santa Anna dissolved the Mexican Congress and set up a dictatorship. Revolts erupted in several Mexican states. After the insurrection spread to Texas in June 1835 (largely because of issues related to the quartering of Mexican soldiers and because of the central government’s collection of customs duties), a group of rebels in Anáhuac seized a Mexican garrison. Anglos Stephen Austin, William Travis, and Sam Houston became leading insurrectionaries. In March 1836, even as the Republic of Texas declared its independence, the Mexican Army under General Santa Anna massacred Texan forces at the Alamo in modern day San Antonio and at Goliad, 100 miles to the southeast.19 But under Sam Houston’s command, the Army of Texas repelled Santa Anna’s divided forces at the Battle of San Jacinto near modern-day Houston, killing roughly half of them and capturing nearly all the rest, including Santa Anna himself. Under the threat of death, Santa Anna ordered his forces to pull out of Texas and across the Rio Grande River, in effect recognizing Texan independence.20

/tiles/non-collection/p/part1_08_houston_sam_lc.xml Image courtesy of the Library of Congress Sam Houston was a prominent war veteran and politician before moving to Texas in 1835. Houston served in the Texas congress and as its first president before his election to the U.S. Senate in 1846.

During the next decade, the population in Texas increased from approximately 30,000 to 50,000 in 1835 to a total of approximately 125,000 to 140,000 in 1845. As members of a distinct minority who were suspected of disloyalty by Anglo settlers, Hispanic Texans were quickly excluded from the political process.21

With the population boom Texas’ first president, Sam Houston, and subsequent leaders sought to join the United States. The Andrew Jackson administration (1829–1837) and the Martin Van Buren administration (1837–1841) demurred despite their unneutrality, fearing that annexation would provoke all-out war with Mexico—inviting a political backlash driven by critics who believed the push for Texas was linked to the extension of slavery in the Southwest.22

But the John Tyler administration (1841–1845) was willing to proceed with annexation. Secretary of State Abel Upshur and his successor, John C.Calhoun, completed the negotiations, which were signed on April 12, 1844, and which made Texas eligible for admission as a U.S. territory, and perhaps later as one or more states. Additionally, the U.S. government assumed $10 million in Texan debt in exchange for public lands. The boundaries with Mexico were left unresolved.23 On June 8, 1844, with public opinion stirred by antislavery activists after Senator Benjamin Tappan of Ohio leaked the provisions of the secret treaty to the press, the Senate rejected it with a vote of 35 to 16. But after the fall 1844 elections, in which James K. Polk triumphed, President Tyler pushed the treaty (H.J. Res. 46) through Congress. It passed the Democratic-controlled House 120 to 98 and the Senate 24 to 21. Tyler signed the treaty into law on March 1, 1845 (5 Stat. 797–798), three days before the end of his term. In the end, Texas was admitted as a state on December 29, 1845, with the proviso that it could be divided into as many as five states—a prospect that outraged and horrified abolitionist members of the Whig Party.24

War with Mexico and the Southwest

/tiles/non-collection/p/part1_09_tx_annexation_roll_call_na.xml Original roll call vote on ratification of treaty to annex Texas; image courtesy of the National Archives and Records Administration On June 8, 1844, the U.S. Senate refused to approve the ratification of a treaty annexing Texas to the United States. Shortly before he left office, President John Tyler, with the support of President-elect James K. Polk, maneuvered a joint resolution through both houses of Congress and signed the annexation treaty into law on March 1, 1845.

James K. Polk set an ambitious course when he assumed the presidency on March 4, 1845.25 A strict Jacksonian, Polk accomplished what later historians have identified as three of four primary goals during the first session of the 29th Congress (1845–1847).26 With the help of Democratic majorities in the House and the Senate, President Polk had lowered the tariff; he had created an independent treasury; and by diplomacy he had acquired the Oregon Territory from England. The acquisition of California from Mexico was all that remained of his original agenda. But unlike the acquisition of Oregon, taking possession of such coveted lands required an all-out war.27

Less than two years into Polk’s presidency, many suspected but few knew about his grand designs for California. Revealing little, Polk sent diplomats to Mexico, pressuring the Mexican government not to interfere with the annexation of Texas. Moreover, Polk claimed that Mexico owed Americans living in Texas millions of dollars for seized and lost property. Mexican officials resisted, banishing Polk’s diplomatic envoy. One historian notes, “Given the anti-American mood of their people, Mexican diplomats understood that any compromise with the United States at this time was tantamount to political suicide.” An anxious Polk ordered U.S. troops to encamp just north of the Rio Grande River in an area that was claimed by both Mexico and the United States. After blockading the river and training its cannon on a nearby town, the U.S. military ignored Mexican requests to stand down. On April 25, 1846, a skirmish between Mexican and U.S. troops ignited hostilities. Mexican officials blamed the United States, while Polk blamed Mexico when he learned of the fighting two weeks later.28 

/tiles/non-collection/p/part1_10_polk_james_lc.xml Image courtesy of the Library of Congress The first Speaker of the House to become President of the United States, James K. Polk was an Andrew Jackson protégé who quickly rose through the ranks of Tennessee politics. During Polk’s term as President (1845–1849), the United States, through war and diplomacy, secured much of the American Southwest and long coveted Pacific Ocean ports along the West Coast.

Polk promptly appealed to Congress for “vigorous & prompt measure[s] to enable the Executive to prosecute the War.”29 Polk asked for 50,000 volunteers because “by the act of the Republic of Mexico, a state of war exists between that Government and the United States.”30 The bill (H.R. 145) met with little open resistance in the House and passed 174 to 14, with only Whigs opposed. Antislavery Whigs, like John Quincy Adams of Massachusetts and Joshua Giddings of Ohio, viewed the war with Mexico as proof that Southern interests intended to expand slavery westward.31Garrett Davis, a moderate Kentucky Whig, was the only one on the floor that day who voiced any opposition to the bill: “It is our own President who began this war,” Davis declared. “He has been carrying it on for months in a series of acts. Congress, which is vested exclusively by the Constitution with war-making power, he has not designed to consult, much less to ask it for any authority.”32 Davis, despite his reservations, voted for the provision of troops and funding.

/tiles/non-collection/p/part1_11_polk_cartoon_lc.xml Image courtesy of the Library of Congress In this 1846 cartoon, President James K. Polk (center left) challenges Senator Daniel Webster of Massachusetts (center right) to a fight because of Webster’s public criticisms of Polk’s Texas policies. Supporters and critics of the war stand behind their respective advocates.

Horrified that the House had passed the bill in under two hours, Senator Thomas Hart Benton of Missouri told Polk that “19th Century war should not be declared without full discussion and much more consideration.”33 Others in the Senate bristled at Polk’s demands. “War could not be made with Mexico,” Senator John Crittenden reminded the body, “without touching the interests and exciting the jealousies of all nations trading with us.” Like the House, the Senate eventually passed the bill with an overwhelming majority, 40 to 2.34 Polk signed it into law (9 Stat. 9–10) the following day, May 13, 1846.

The war’s nominal popularity in Congress disguised many people’s reservations. Andrew Jackson Donelson, the former President’s nephew, advised Polk to resolve the trouble quickly. “Nothing can be gained by a war with Mexico,” he said. “We are not ready for another Annexation question, and the Mexicans are not fit for incorporation into our Union.”35 In the House, Giddings finally lambasted the war. It would, he noted, be long, expensive, and disgraceful, and given its “connection with slavery,” he said, it threatened the “harmony and perpetuity of the Union.”36  

Treaty of Guadalupe Hidalgo

/tiles/non-collection/p/part1_12_pueblo_indians_lc.xml Image courtesy of the Library of Congress A Zia Pueblo family was photographed in the New Mexico Territory in 1885.

The Treaty of Guadalupe Hidalgo, signed by chief negotiator Nicholas P. Trist on February 2, 1848, and approved by the U.S. Senate on March 10, 1848, ended the war, opened a dramatically different chapter in U.S. relations with Mexico, and nearly completed America’s continental empire.37 The war, however, was not without cost; roughly 12,500 U.S. troops died (most from disease), and the federal government spent nearly $100 million.38 Moreover, stiff Mexican resistance on the battlefield and at the negotiating table made the conflict last longer than the Polk administration anticipated. Popular support waned as the conflict continued, contributing to a change in control; the House flipped to a new Whig majority in the 1846 elections.39 Moreover, “Mr. Polk’s War” brought the country closer to fratricidal conflict: Would the new territories permit or outlaw slavery?

Even counting the human, financial, and political costs of the war, the Treaty of Guadalupe Hidalgo represented an American bonanza purchased at a discount. For the equivalent of nearly one-third of the landmass of the modern continental United States, American officials paid $15 million to Mexico and assumed $3.25 million in war claims by U.S. citizens.40 In one fell swoop, America gained control of 530,000 square miles. From Mexico’s vantage point, the United States gained over 900,000 square miles, including disputed Texas land claims Mexico had long considered illegitimate. The United States obtained nearly all of modern-day New Mexico and Arizona (whose southern portions were later acquired in the 1853 Gadsden Purchase); all of Nevada, Utah, and California, with its coveted deep water ports on the Pacific Ocean; and portions of present-day Colorado and Wyoming.41 The war also engendered resentment among Mexicans and other Latin Americans, leaving many wary of U.S. motives.42

/tiles/non-collection/p/part1_13_guadalupe_hidalgo_map_na.xml E. Gilman, Map of the United States Including Western Territories, map (Philadelphia: P.S. Duval’s Steam Lith. Press, 1848); from National Archives and Records Administration, Records of the U.S. House of Representatives, RG 233 This 1848 map outlines the territories acquired by the United States in the Treaty of Guadalupe Hidalgo. The borders of California, New Mexico, and Texas were later formalized as part of the Compromise of 1850.

The Treaty of Guadalupe Hidalgo also began to address practical issues that arose from the fact that roughly 90,000 Mexican citizens, and substantially more American Indians of various tribes, were living in the newly acquired lands, most of them in what became modern-day New Mexico.43 The treaty contained provisions pertaining to Mexican citizens—a group that included the nonitinerant Pueblo Indians—which guaranteed their U.S. citizenship and property rights, and permitted indigenous peoples to retain or renounce their Mexican citizenship in favor of U.S. citizenship. The treaty also extended blanket U.S. citizenship to any individual who had not made a declaration within one year of its ratification.

But these guarantees were qualified. For instance, Pueblos, although they were Mexican citizens, were not accorded full civil and political rights. Instead, they were treated like the members of other Indian tribes in U.S. territory, who would eventually be moved to reservations and would not participate in territorial politics. For decades, congressional debates about New Mexican statehood were dominated by the question of whether nuevomexicanos were white enough to achieve self-government, leading many Hispano politicians to accentuate their Spanish ancestry and to differentiate themselves from their Mexican and American Indian constituents.44

The Senate’s consideration of the treaty amplified the calls of Manifest Destiny.45 Thomas Ritchie, editor of the pro-Polk Washington Daily Union, wrote, “What we desire to obtain from Mexico is more of territory and less of population, but we have no objection to the acquisition of a few of her people along with the soil which we get.” Senator Daniel S. Dickinson of New York explained that a “majority” of nuevomexicanos were members of “fated aboriginal races” who could “neither uphold government or be restrained by it” and therefore must “perish under, if they do not recede before, the influences of civilization.”46 Given prevailing racial prejudices and lingering concerns about the Catholicism of the Mexicans in the Southwest, the promises of citizenship as outlined by the treaty remained for decades largely unresolved, particularly in territories such as New Mexico and Arizona.

Why did the US turn to a policy of expansionism?

Why did the US follow a policy of expansionism in the late 1800s?