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By the end of this section, you will be able to:
  • Identify the causes of the Mexican-American War
  • Describe the outcomes of the war in 1848, especially the Mexican Cession
  • Describe the effect of the California Gold Rush on westward expansion

Tensions between the United States and Mexico rapidly deteriorated in the 1840s as American expansionists eagerly eyed Mexican land to the west, including the lush northern Mexican province of California. Indeed, in 1842, a U.S. naval fleet, incorrectly believing war had broken out, seized Monterey, California, a part of Mexico. Monterey was returned the next day, but the episode only added to the uneasiness with which Mexico viewed its northern neighbor. The forces of expansion, however, could not be contained, and American voters elected James Polk in 1844 because he promised to deliver more lands. President Polk fulfilled his promise by gaining Oregon and, most spectacularly, provoking a war with Mexico that ultimately fulfilled the wildest fantasies of expansionists. By 1848, the United States encompassed much of North America, a republic that stretched from the Atlantic to the Pacific.

James k. polk and the triumph of expansion

A fervent belief in expansion gripped the United States in the 1840s. In 1845, a New York newspaper editor, John O’Sullivan, introduced the concept of “manifest destiny” to describe the very popular idea of the special role of the United States in overspreading the continent—the divine right and duty of white Americans to seize and settle the American West, thus spreading Protestant, democratic values. In this climate of opinion, voters in 1844 elected James K. Polk, a slaveholder from Tennessee, because he vowed to annex Texas as a new slave state and take Oregon.

Annexing Oregon was an important objective for U.S. foreign policy because it appeared to be an area rich in commercial possibilities. Northerners favored U.S. control of Oregon because ports in the Pacific Northwest would be gateways for trade with Asia. Southerners hoped that, in exchange for their support of expansion into the northwest, northerners would not oppose plans for expansion into the southwest.

President Polk—whose campaign slogan in 1844 had been “Fifty-four forty or fight!”—asserted the United States’ right to gain full control of what was known as Oregon Country, from its southern border at 42° latitude (the current boundary with California) to its northern border at 54° 40' latitude. According to an 1818 agreement, Great Britain and the United States held joint ownership of this territory, but the 1827 Treaty of Joint Occupation opened the land to settlement by both countries. Realizing that the British were not willing to cede all claims to the territory, Polk proposed the land be divided at 49° latitude (the current border between Washington and Canada). The British, however, denied U.S. claims to land north of the Columbia River (Oregon’s current northern border) ( [link] ). Indeed, the British foreign secretary refused even to relay Polk’s proposal to London. However, reports of the difficulty Great Britain would face defending Oregon in the event of a U.S. attack, combined with concerns over affairs at home and elsewhere in its empire, quickly changed the minds of the British, and in June 1846, Queen Victoria’s government agreed to a division at the forty-ninth parallel.

Questions & Answers

Which of the following protests was directly related to federal policies, and thus had the biggest impact in creating a negative public perception of Hoover presidency
Steven Reply
the Bonus Army
Victor
what mistakes did Britain mak the lost them the colonies
Victor Reply
tax without representation
JOE'S
they did not give the colinies any representation
Victor
the american revolution
Angelica Reply
what started the American revolution
Futuremfan
immediate cause: British tried to seize weapons stored by local militia which led to a confrontation
Victor
hi...can you state benefit of U.S constitution
Chimi Reply
bill of rights
Tom
it provided a political framework which provifed stability while at the same time permitting freedoms which allowed the American people to flourish
Victor
Among the major cause of American civil war, can I have a brief account on social cause?
Rinchen Reply
The issue of slavery between South America and North America that lead to the American Civil War
Sanusi
not sure what you mean by "social" causes. Do you mean things like differences between Northern ers & southerners?
Victor
what was the purpose of Operation Valkyrie?
Matthew Reply
I have no idea
Sanusi
that was the WWII attempt by German officers to overthrow Hitler.
Victor
which culture developed the writting system in the western hemisphere?
cierra Reply
the phoenicians
Victor
Treaty of Greenville
The Reply
By this treaty Indians gave up some land in exchange for am annuity of money & supplies. It followed Battle of Fallen Timbers, a decisive victory of US troops over Indian tribes organized into the Western Confederacy. It marks the beginning of modern state of Ohio.
Victor
Please keep in mind that it is not allowed to promote any social groups (whatsapp, facebook, etc...) or exchange phone numbers or email addresses on our platform.
QuizOver Reply
Columbus didn't discover ish. He stole America from the Natives
LovingN Reply
Who was Nat Turner? What was the cause and impact of the Nat Turner Rebellion?
LovingN
which culture developed the only writing systems in the western hemisphere
rose Reply
economic causes of American civil war
Samten Reply
do you mean the major causes of American civil war
CHEGWE
yes
Samten
idealistic birth of industries in great britain
Rinchen Reply
how doent show that Martin king jr dies where say that on google.com
Jessica Reply
what year was America found
Adaregba Reply
i think America was discovered by Christopher Columbus in the year 1492
Samten
yes samten ,it was discovered by Christopher Columbus in August 3rd 1492
CHEGWE
but, we're was the name (America gotten from
CHEGWE
i could't understand what are you asking about
Samten
sorry i don't have this answer
Samten
ok
CHEGWE

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Source:  OpenStax, U.s. history. OpenStax CNX. Jan 12, 2015 Download for free at http://legacy.cnx.org/content/col11740/1.3
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