- [Kim] This is a painting
of US general Winfield Scott
entering Mexico City on September 15th, 1847.
Scott landed with a US naval fleet several weeks beforehand.
He bombarded the coastal stronghold of Veracruz
and then fought his way inland toward the capital.
Scott actually followed the same route
that Spanish conquistador Hernan Cortes took
more than 300 years earlier.
Winfield Scott's campaign to Mexico City
was just one of three fronts
in the two-year-long, continent-spanning effort
of the United States to take Mexican territory by force.
The other two fronts were in California and New Mexico.
After the two nations made peace
by signing the Treaty of Guadalupe Hidalgo in mid 1848,
the United States gained over a million square miles
of new territory,
a landmass larger than the Louisiana Purchase.
For Mexico, this war was a catastrophic defeat,
which resulted in the loss of about 1/3 of its total area.
The Mexican-American War doesn't really loom large
in American memory, compared to the Revolutionary War
or the Civil War, but it was a transformative event
in the history of the United States and North America.
On the scale of national politics,
the war led to political realignment,
and eventually, the Civil War.
But on a human scale, it led to transformations
in the lives of people who lived in the West
who went to bed one day in Mexico
and woke up the next day in the United States.
National boundaries shifted under their feet.
For those people, the outcome of the war meant new laws,
customs, new friends and enemies,
and even the loss of rights and privileges.
So let's dive a little deeper into the causes and effects
of the Mexican-American War.
The war began in April of 1846.
A Mexican cavalry brigade attacked US forces
who were under the command of General Zachary Taylor
across the Rio Grande River
from the town of Matamoros, Mexico.
After this attack, President James K. Polk
sent a war message to Congress.
He fumed that the Mexican troops had invaded our territory
and shed American blood on American soil.
Now back up a minute.
You may be wondering,
as many keen observers did at the time,
what exactly were US forces doing there
near Rio Grande River in the first place?
And the answer to that reveals the two major causes
of the war, Texas annexation and Manifest Destiny.
Let's start by talking about Texas annexation.
American settlers, many of whom were slave owners,
had been moving to Texas since the 1820s,
when the region was still controlled by Spain.
After Mexican independence, the country outlawed slavery.
But the American settlers resisted
the Mexican government's authority.
In 1836, they rebelled and won independence for Texas.
They requested the United States annex the new nation
shortly thereafter, but adding another slave state
to the Union was politically dangerous
for the administration at that time.
So Texas remained an independent nation until 1845.
In 1845, Democratic president James K. Polk took office.
Now Polk was an ardent expansionist.
He was a believer in Manifest Destiny,
this idea that God wanted the United States
to expand across the North American continent.
Polk wanted to annex Texas,
which his administration undertook immediately.
He also desperately wanted California,
which was a hub of commerce on the Pacific Ocean.
This is actually before gold was discovered there.
So Polk sent a representative to the Mexican government
offering to buy California.
But Mexico said California was not for sale.
Now Polk was determined to get this territory
with blood or money.
So he came up with an alternate plan.
The border between Mexico and Texas was under dispute.
So Polk directed General Zachary Taylor
to go down into this disputed territory
and provoke hostilities.
And that's exactly what happened
when the Mexican cavalry attacked Taylor's forces.
As far as Mexico was concerned,
Taylor's troops were invading their country,
and they had no choice but to defend it.
Despite Polk's war message saying that
American blood had been shed on American soil,
many US politicians were also skeptical about
who started the war and where.
A young Whig congressman from Illinois named Abraham Lincoln
demanded that Polk show him the exact spot
where American blood had been shed.
The war that ensued was longer, costlier, and deadlier
than the US government had estimated,
which is often the case with wars.
At its conclusion, Polk had achieved his vision
for Manifest Destiny.
In the Treaty of Guadalupe Hidalgo, which ended the war,
the United States agreed to pay Mexico $15 million,
and in exchange, Mexico ceded Texas, California,
and most of the modern-day Southwest to the United States.
So what were the effects of this war?
Well, the addition of this Mexican cession territory
had far-reaching consequences for both the United States
and the residents of the West.
The existing resident of the territory,
including Mexicans, Native Americans,
and the descendants of Spanish colonists,
found that life under the rule of the United States
could be very different than under the rule of Mexico.
Where Mexican law had abolished slavery
and proscribed equality under the law
for people regardless of color,
the Texas constitution permitted slavery
and denied civil rights to non-white residents.
For other residents of the territory,
life didn't change much at all.
Huge swathes of the West were actually controlled
by Native American nations, like the Comanche Empire,
which didn't care whether the distant government
who claimed their territory on paper
was located in Mexico City or in Washington DC.
For the United States government,
the addition of this new territory was political kryptonite.
Both Northerners and Southerners were convinced
that the opposite region was conspiring
to limit their economic opportunities in the West.
During the war, Congressman David Wilmot of Pennsylvania
introduced a resolution in the House
that would prohibit slavery
in any territory gained from the conflict.
The reaction to the Wilmot Priviso
showed just how big the sectional divide in the country
was becoming, since party lines broke down entirely.
Northerners, Whig, and Democrat alike
voted for the Wilmot Proviso,
and Southerners, Whig, and Democrat alike voted against it.
Ultimately, the proviso passed in the House
was defeated in the Senate.
And then gold was discovered in California,
just before the end of the war,
sending hordes of prospectors West
and making statehood for California an urgent issue
that would soon upset the balance of power
between free and slave states in Congress.
In other words, we can draw a direct line
from the Mexican War
to the breakdown of the second party system,
which was replaced by a solidly Southern Democratic party
and a new Northern Republican party,
and from there to the Civil War.