Was ‘manifest destiny’ an American policy or merely a partisan slogan?

CHAPTER 5: A Dose of Arsenic: Slavery, Expansion, and the Road to Disunion, 1837-1861

“American expansionism in the 1840s was neither providential nor innocent. It resulted from design, rather than destiny, a carefully calculated effort by purposeful Democratic leaders to attain specific objectives that served mainly U.S. interests.  The rhetoric of Manifest Destiny was nationalistic, idealistic, and self-confident, but it covered deep and sometimes morbid fears for America’s security against internal decay and external danger.  Expansionism showed scant regard for the ‘inferior’ peoples who stood in the way.  When combined with the volatile issue of slavery, it fueled increasingly bitter sectional and partisan conflict.”

–George C. Herring, From Colony to Superpower:  U.S. Foreign Relations Since 1776 (New York: Oxford University Press, 2008), 184.

  • KEY TERMS & FIGURES: Manifest Destiny (1845) // Mexican War (1846-47) // John O’Sullivan // James Polk // James Buchanan // Townsend Harris // William Walker
Manifest Destiny map

From the Manifest Destiny layer (1815-1900) in the course map of Herring’s book. Can you identify these place marks? What other relevant place marks for US global expansion might be included for this time period?


Jackson, O'Sullivan, Polk

James Buchanan with James Polk’s Family

[SOURCE: Allan Nevins, ed., Polk: The Diary of a President, 1845-1849 (London: Longmans, 1952), 89-91]

Other Key Players, Witnesses, or Examples

“Three T’s” of Nineteenth-century US Expansionism

  • Territory
  • Trade
  • Transnationalism

KEY TERMS:  Manifest Destiny (1845) // Mexican War (1846-47)

“The catchphrase ‘Manifest Destiny’ summed up the expansionist thrust of the pre-Civil War era.  Coined in 1845 by the Democratic Party journalist John L. O’Sullivan to justify annexation of Texas, Oregon, and California, the phrase meant, simply defined, that God had willed the expansion of the United States to the Pacific Ocean –or beyond.  The concept expressed the exuberant nationalism and brash arrogance of the era.  Divine sanction, in the eyes of many Americans, gave them a superior claim to any rival and lent an air of inevitability to their expansion.  Manifest Destiny pulled together into a potent ideology notions dating to the origins of the republic with implications extending beyond the continent: that the American people and their institutions were uniquely virtuous, thus imposing on them a God-given mission to remake the world in their own image.  Many Americans have accepted the rhetoric of Manifest Destiny at face value, seeing their nation’s continental expansion as inevitable and altruistic, a result of the irresistible force generated by a virtuous people.  Once viewed as a great national movement, an expression of American optimism and idealism, and the driving force behind expansion in the 1840s.  Manifest Destiny’s meaning and significance have been considerably qualified in recent years.” –George Herring, From Colony to Superpower (2008), p. 180

Gast painting

Discussion Questions

  • Herring labels “Manifest Destiny” (which he usually capitalizes) as both “a catch-phrase” and “a potent ideology.”  But after reading his chapter, would you also label it as official US policy during the 1840s?
  • By the outbreak of Civil War in 1861, which side held the upper hand in the national debate: advocates for manifest destiny, or those who were more skeptical of territorial expansion?

Additional Resources

Origins of the term “manifest destiny” (1845)

On Texas (July 1845)

“…other nations have undertaken to intrude themselves into it, between us and the proper parties to the case, in a spirit of hostile interference against us, for the avowed object of thwarting our policy and hampering our power, limiting our greatness and checking the fulfillment of our manifest destiny to overspread the continent allotted by Providence for the free development of our yearly multiplying millions.” –Excerpted from John L. O’Sullivan, “Annexation,” The United States Magazine and Democratic Review 17 (July 1845): 5–10

On Oregon (December 1845)

“…that claim is by the right of our manifest destiny to overspread and to possess the whole of the continent which Providence has given us for the development of the great experiment of Liberty.”  –Excerpted from John L. O’Sullivan, New York Morning News, December 27, 1845 (see also Herring, 191)

Mexican War (1846-48)

“The Mexican-American War resulted from U.S. impatience and aggressiveness and Mexican weakness.  Polk and many of his countrymen were determined to have Texas to the Rio Grande and all of California on their own terms.  They might have waited for the apples to fall from the tree, to borrow John Quincy Adams’s Cuban metaphor, but patience was not among their virtues.  Polk appears not to have set out to provoke Mexico into what could be used as a war of conquest.  Rather, contemptuous of his presumably inferior adversaries, he assumed he could bully them into giving him what he wanted.  Mexico’s weakness and internal divisions encouraged his aggressiveness.  A stronger or more united Mexico might have deterred the United States or acquiesced in the annexation of Texas to avoid war, as the British minister and former Mexican foreign minister Lucas Alaman urged.  By this time, however, Yankeephobia was rampant.  Mexicans deeply resented the theft of Texas and obvious U.S. designs on California.  They viewed the United States as the ‘Russian threat’ of the New World.  Incensed by the racist views of their northern neighbors, they feared cultural extinction.  Newspapers warned that if the North Americans were not stopped in Texas, Protestantism would be imposed on the Mexican people and they would be ‘sold as beasts.’  Fear, anger, and pride made it impossible to acquiesce in U.S. aggression.  Mexico chose war over surrender.”  –George Herring From Colony to Superpower (2008), p. 199-200

Discussion Questions

  • The way Herring characterizes the rush to war in 1846 suggests that he considers many of the key decisions to be irrational.  Do you find this persuasive after learning more about the context of that crisis moment?
  • What were some of the unintended consequences of the US-Mexican War?

War map


Excerpt from the Diary of James K. Polk, May 13, 1846 (the day Congress declared war on Mexico)

Then, said Mr. Buchanan, you will have war with England as well as Mexico, and probably with France also, for neither of these powers will ever stand by and see California annexed to the United States.

Wednesday, 13th May, 1846

…Most of the Cabinet were in attendance, though no Cabinet meeting had been called. A proclamation announcing the existence of the war was prepared and signed by me. This was done in pursuance of the precedent of Mr. Madison, in 1812…Mr. Buchanan read the draft of a despatch which he had prepared to our Ministers at London, Paris, and other foreign courts, announcing the declaration of war against Mexico, with a statement of the causes and objects of the war, with a view that they should communicate its substance to the respective governments to which they are accredited. Among other things Mr. Buchanan had stated that our object was not to dismember Mexico or to make conquests, and that the Del Norte was the boundary to which we claimed; or rather that in going to war we did not do so with a view to acquire either California or New Mexico or any other portion of the Mexican territory.

I told Mr. Buchanan that I thought such a declaration to foreign governments unnecessary and improper; that the causes of the war as set forth in my message to Congress and the accompanying documents were altogether satisfactory. I told him that though we had not gone to war for conquest, yet it was clear that in making peace we would if practicable obtain California and such other portion of the Mexican territory as would be sufficient to indemnify our claimants on Mexico, and to defray the expense of the war which that power by her long continued wrongs and injuries had forced us to wage. I told him it was well known that the Mexican Government had no other means of indemnifying us.

Then, said Mr. Buchanan, you will have war with England as well as Mexico, and probably with France also, for neither of these powers will ever stand by and see California annexed to the United States.

…Towards the close of the discussion, which lasted for more than two hours, I stepped to my table and wrote a paragraph to be substituted for all that part of Mr. Buchanan’s proposed despatch which spoke of dismembering Mexico, of acquiring California, or of the Del Norte as the ultimate boundary beyond which we would not claim or desire to go. I strongly expressed to Mr. Buchanan that these paragraphs in his despatch must be struck out. Mr. Buchanan made no reply, but before he left took up his own draft and the paragraphs which I had written and took them away with him. I was much astonished at the views expressed by Mr. Buchanan on the subject. The discussion tonight was one of the most earnest and interesting which has ever occurred in my Cabinet. [SOURCE: Allan Nevins, ed., Polk: The Diary of a President, 1845-1849 (London: Longmans, 1952), 89-91]

Additional Resources on the Mexican War