Lecture: Manifest Destiny & Expansion
Lecture script · about 15–20 minutes spoken · Week 11
Opening
Think about a future teacher in a community whose families lived on their land before a border crossed them. Or think about a law student reading what a treaty promised, and what it left out. Both of them face one question. When a country grows, who gains, and who pays? That's the question at the center of this lecture.
In Week 1 you learned the four moves for reading a source: sourcing, contextualization, close reading, and corroboration. In Week 5 you read the Declaration of Independence. In Week 9 you followed the Louisiana Purchase and the removal of Native nations from the Southeast. In Week 10 you followed the reformers of the same decades.
Here's this lecture's story in one line. Between 1836 and 1848 the United States grew from the Mississippi to the Pacific. Texas broke from Mexico and joined the Union. Britain and the United States split Oregon. A war with Mexico ended in a treaty that moved the border far to the south. We'll read two documents on the way, a declaration and a treaty. And I'll keep asking you the same thing about each one: who wrote it, and who was left out?
1. A phrase, not a law: manifest destiny
Think about a slogan on a campaign button. It doesn't pass a law or sign a treaty. It gives people a reason to cheer for something they already want.
In 1845 an editor named John L. O'Sullivan used a phrase for the belief that the country was destined to spread across the continent. Manifest destiny is a phrase the editor John L. O'Sullivan used in 1845 for the belief that the United States was destined to spread across the continent; supporters used it to justify expansion, and it was never a law or an official policy. No Congress passed it. No treaty contains it. In this course we treat it as a phrase people used, not as our own way of seeing the past.
The phrase rode on top of a real movement. Families loaded wagons and crossed to Oregon on the Oregon Trail, the overland wagon route that carried emigrant families from the Missouri River to the Oregon country in the 1840s. That trail crossed other people's homelands. The National Park Service writes that each year brought more emigrants who wanted Native land. The Cayuse Nation's homeland lay on that route, and the park service tells the Cayuse story in partnership with the Confederated Tribes of the Umatilla Indian Reservation.
So here's the habit I want you to build. When you meet a big phrase in a source, ask who said it, and ask whether any law or treaty contains it. A phrase can explain why people wanted something. It can't tell you how they got it. Laws, treaties, and armies did the getting.
Pause and try this. A newspaper editorial says the country is destined to reach the Pacific. Is that editorial a law?
Picture the editorial on the printer's desk.
Here's the answer. No, it's a reason someone gives for expansion, because no Congress passed it and no treaty contains it.
2. A declaration and a silence: Texas in 1836
Picture a group of tenants writing to a landlord to list every broken promise. The letter is honest about what angers them. It can still leave out the thing the tenants are doing that the landlord objects to.
Texas in the 1830s was part of Mexico. Mexico's colonization laws had invited settlers from the United States into Texas, and the Texas declaration itself says so. Some settlers brought enslaved people with them. The Texas State Library and Archives Commission explains that slavery was illegal under Mexican law, but Mexican officials never stopped American slaveholders from bringing enslaved people into Texas.
Now the document. The Texas Declaration of Independence is the declaration that the delegates of the people of Texas adopted in convention at Washington-on-the-Brazos in 1836, listing grievances against Santa Anna's government and declaring Texas independent of Mexico. Let's source it. The delegates made it, the Avalon Project keeps it, and the State Library says George Childress is generally accepted as its author. The State Library also says 59 delegates approved it. Among them was J. Antonio Navarro, a Tejano born in San Antonio. Tejanos are Mexican Texans, the Spanish-speaking people of Texas whose families lived there under Spain and Mexico, some of whom took part in the Texas Revolution.
Close reading comes next. The grievances include trial by jury, public schooling, religion, and arms. The pinned passage calls jury trial "the right of trial by jury, that palladium of civil liberty". A palladium is a safeguard. Then ask what's missing. The word slave does not appear in Avalon's text at all.
Corroboration fills the silence. The State Library writes that about 5,000 enslaved African Americans lived in Texas in 1836, and that the Constitution of the Republic of Texas protected slavery. So the plain sentence goes like this. The declaration shows the grievances its delegates named against Santa Anna's government in 1836; its silence about slavery is not evidence that slavery was absent from Texas.
Pause and try this. If a declaration never mentions slavery, does that show slavery wasn't part of the story?
Think about what corroboration added.
Here's the answer. No, because the State Library's record shows thousands of enslaved people in Texas and a constitution that protected slavery.
3. Two routes to a state: annexation and Oregon
Think of two neighbors arguing over a fence. One wants to buy the yard next door, and the owner won't sell. Far down the street, you share a garden with a third neighbor, and you both want the whole plot.
Annexation is the act of one country adding another territory to itself, as the United States added the Republic of Texas in 1845. The Office of the Historian, the State Department's history office, writes that the President recognized Texas but held back from annexation, because Mexico threatened war. The State Library adds why the question came back. Britain had offered Texas a loan that would let it free its enslaved people, and Southern planters feared a free Texas under British influence.
Here's the route. In 1844 a treaty of annexation went to the Senate and failed. You read the Constitution in Week 6, and it requires two-thirds of the Senate to approve a treaty. So in 1845 Congress used a joint resolution, a measure passed by simple majorities in both houses of Congress. It passed, and Texas entered the Union as a state where slavery was protected.
Oregon was the shared garden. The United States and Britain had shared the Oregon country, and some Americans demanded the whole territory up to 54 degrees 40 minutes. The Oregon Treaty is the treaty of 1846 in which the United States and Britain divided the Oregon country at the 49th parallel. Notice who signed it: two governments. The nations who lived there weren't at the table.
Pause and try this. Why did it matter that Congress used a joint resolution instead of a treaty?
Think about what each one needed to pass.
Here's the answer. A treaty needed two-thirds of the Senate and had failed, while a joint resolution needed only simple majorities.
4. A contested war: the U.S.-Mexican War
Picture a town newspaper in 1846 with two letters on one page. One reader calls the war a defense of American soil. The other asks whether the soil was American at all.
The U.S.-Mexican War is the war between the United States and Mexico from 1846 to 1848, which began over the disputed Texas border and ended with the Treaty of Guadalupe Hidalgo. Texas claimed the Rio Grande as its border. Mexico said the border was the Nueces River, farther north. The land between is the Nueces Strip.
Follow the steps the National Park Service gives. President James K. Polk ordered General Zachary Taylor's army into the strip, land that Mexico and many Americans held was never part of Texas. American guns and ships blockaded the Mexican city of Matamoros. Mexican forces crossed the river to break the blockade and fired on a small American force. Polk told Congress that Mexico had invaded American soil, and Congress declared war in 1846.
I'll say the war's violence plainly, because it belongs in the record. The park service writes that sexual assault, looting, and killings of civilians and surrendered Mexican soldiers were common as American forces advanced. U.S. forces took Mexico City within 16 months.
And not everyone cheered. Abraham Lincoln, then a congressman, demanded proof that the war began on American soil. Henry David Thoreau went to jail rather than pay taxes that supported the war. Expansion was argued over at the time.
Pause and try this. Was the war with Mexico something every American supported?
Think of the congressman and the writer.
Here's the answer. No, because Lincoln challenged where it began and Thoreau went to jail rather than pay for it.
5. The treaty of peace: Guadalupe Hidalgo
Think about the papers that change hands when a house is sold. The deed names the buyer, the seller, the price, and the lines. It may promise something to the people renting the upstairs rooms. Whether that promise is kept is another story.
The Treaty of Guadalupe Hidalgo is the treaty of peace between the United States and the United Mexican States signed at Guadalupe Hidalgo in 1848, which ended the U.S.-Mexican War and transferred Mexico's northern territories to the United States. It's this week's Primary Source Workshop document.
Let's source it. Two governments made it. It's a treaty of peace, and its closing line dates the signing 2 February 1848 at Guadalupe Hidalgo. The Avalon Project keeps the text, and the National Archives keeps the exchange copy in Spanish and English. Here's a dating trap. Avalon's page heading also lists later steps that same year: the Senate's advice, the exchange of ratifications at Querétaro, and the proclamation. You date the treaty from its own closing line, as Week 5 taught you with the Treaty of Paris.
Now close reading. Article XII paid Mexico 15,000,000 dollars. The Office of the Historian and the National Archives both say Mexico ceded about 525,000 square miles, 55 percent of its territory. Article VIII is the article of the Treaty of Guadalupe Hidalgo that let Mexicans living in the ceded lands stay or move to Mexico with their property and gave them one year to choose Mexican or United States citizenship. Its pinned passage says they "shall be free to continue where they now reside, or to remove at any time to the Mexican Republic". And the Senate struck out Article X, which had protected Mexican land grants.
So here's the plain sentence. The treaty shows what two governments promised about the ceded lands and the Mexicans living there in 1848; it is evidence of those promises, not of whether they were kept, and not of what any Native nation agreed.
Pause and try this. Did the treaty turn the Mexicans already living in the ceded lands into immigrants?
Think about who moved, the people or the line.
Here's the answer. No, because they stayed where they were and the border moved over them, which is why Article VIII treats them as people already established there.
6. Who was left out: Native nations
This part describes disease, violence, and many deaths. Take it at your own pace.
Picture two neighbors signing an agreement about a third neighbor's land. The third neighbor isn't in the room, and the paper mentions that neighbor only once, as a problem to manage.
No Native nation signed the Treaty of Guadalupe Hidalgo. Here's the one place the treaty speaks of them. Article XI is the article of the Treaty of Guadalupe Hidalgo in which the United States promised to restrain raids into Mexico by Native peoples of the ceded lands. It described them only as tribes, never as parties to the treaty. I'm not quoting its words, because they use the language of its time.
Two federal records show what came next. The National Library of Medicine writes that Miwok, Maidu, and Nisenan people helped dig the millrace at Sutter's Mill, where gold was found in 1848. That set off the California Gold Rush. The miners who followed brought diseases that killed thousands of Native people, and miners attacked Native villages across California and Oregon. In Oregon, the National Park Service writes that a group of Cayuse people attacked the Whitman mission in 1847, after epidemics had brought widespread death. The government then used the attack as an excuse to set up reservations.
Historians revise their estimates of how many people died, so this course teaches the loss in words and asks you to memorize no figure. And these are nations now, not only nations then. The Cayuse, Umatilla, and Walla Walla peoples govern themselves as the Confederated Tribes of the Umatilla Indian Reservation.
Pause and try this. Which Native nations signed the Treaty of Guadalupe Hidalgo?
Think about who was at the table.
Here's the answer. None did, because only the United States and Mexico were parties, and Article XI wrote about Native peoples without them.
7. An old rule meets new land: the Wilmot Proviso
Think about a house rule written for one room. Then the family builds a new wing. The rule never mentioned the wing, so the argument starts over.
In Week 9 you read the Missouri Compromise row of the territories set. It barred slavery north of 36 degrees 30 minutes, but only in the rest of the Louisiana Purchase. The land taken from Mexico lay outside the Louisiana Purchase. So that line said nothing about it.
In 1846, while the war was still being fought, Congressman David Wilmot proposed a rider. The Wilmot Proviso is the rider Congressman David Wilmot proposed in 1846 to bar slavery from any territory the United States acquired in the war with Mexico; Southern senators blocked it. The Office of the Historian writes that the fight over slavery's expansion went on until 1865. I'll stop the story there. How Congress handled the new land in 1850 is next week's subject.
Pause and try this. Did the Missouri Compromise line decide slavery in the land taken from Mexico?
Think about which land the line covered.
Here's the answer. No, because it covered only the rest of the Louisiana Purchase, and the new land lay outside it.
8. Order the years and sort two claims
Picture two folders on a shelf, one marked 1836 and one marked 1848. Two older folders from Week 5 and Week 9 sit beside them.
Let's put them in order. The Texas declaration of 1836 comes before the treaty of 1848. From one to the other is 12 years. From the Louisiana Purchase Treaty of 1803 to the treaty of 1848 is 45 years. From the Declaration of Independence of 1776 to the Texas declaration is 60 years.
Now match the passages. "the right of trial by jury, that palladium of civil liberty" comes from the Texas declaration. "shall be free to continue where they now reside, or to remove at any time to the Mexican Republic" comes from the treaty. That's one passage from each document, 2 in all.
Last, sort two illustrative claims. The first says the Texas declaration lists the failure to secure trial by jury among its grievances. That shows what the source says. The second says the Texas Revolution was fought only over trial by jury. That goes beyond the source.
Pause and try this. Why does the second claim go beyond the source?
Think about what else the declaration lists, and what it leaves out.
Here's the answer. Because the declaration names many grievances and stays silent on slavery, so no single grievance can be the whole cause.
Closing
Let me pull it together. Manifest destiny was a phrase people used to justify expansion, never a law. The Texas declaration of 1836 named many grievances and never used the word slave, and the State Library's record fills that silence. Texas joined the Union by joint resolution, and Oregon was split at the 49th parallel. The war with Mexico began on disputed land, was opposed at home, and brought violence to Mexican civilians. The Treaty of Guadalupe Hidalgo moved the border; the people stayed, and Article VIII let them choose. No Native nation signed it, and the Gold Rush brought disease and violence to California's Native peoples. The Wilmot Proviso showed the new land had reopened the slavery question.
Next in this module come the slide deck, the Readings & Resources page, the lecture tutorial, the practice set, and the quiz. Next week, in Week 12, the course turns to slavery and the sectional crisis, and the land won from Mexico is where that crisis begins.
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