Mexican War 1846-1848
Causes of the Mexican War
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Manifest Destiny
Texas Annexation by the United States
Boundary dispute between Mexico and
the U.S. over the boundary of Texas
Manifest Destiny
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Belief that God has said America has a
right and duty to expand and stretch
from the East Cost to the Pacific Coast
US felt they had a mission to shares
its ideas on democratic institutions
Reasons Behind Manifest Destiny
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Population Increase
Economic depressions—1818 and 1839
Abundance of cheap (or free) land in
West.
Expansion offered opportunities for new
commerce.
Manifest Destiny . . .
JOHN GAST‘S - "AMERICAN PROGRESS," (1872)
Mexican American War
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It all starts with Texas.
At first Mexicans encourage American
settlement.
Conflicts over slavery issues
Americans who live there are rebellious
bunch—start to clamor for independence.
Key Figures in Texas Independence 1836
Sam Houston
(1793-1863)
Steven Austin
(1793-1836)
The Battle of the Alamo
General
Antonio de
Santa Ana
recaptures
the Alamo
Texas Declaration of Independence
The
Republic of
Texas
Victory in Texas
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Santa Anna forced to sign Treaty of
Velasco—1836.
Texas becomes independent.
Americans wait ten years to annex
Texas—because of issue of slavery and to
avoid war with Mexico.
Texas Annexation
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March 1845 Congress approves Texas
Annexation
Texas becomes the 28th state in
December of 1845.
Mexico reacts by cutting off all
diplomatic ties with the U.S.
Boundary Dispute
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Texas and U.S. claim that the Rio
Grande marks the southern border of
Texas
Mexican government rejects this idea
and argues that the real southern
border is the Nueces River
Rio Grande boundary
Nueces River boundary
Polk’s War Strategy
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General Zachary Taylor
invaded northern
Mexico.
General Stephen
Kearny traveled west
and captured Sante Fe,
and supported revolt in
California.
General Winfield Scott
invaded Mexico City.
Steps to War
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June 1845- President
Polk ordered General
Zachary Taylor to
take U.S. troops into
disputed border
region
Polk claims this action
is to protect Texas
from possible Mexican
attack
James K. Polk
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The “dark horse”
candidate from
Tennessee wins the
election of 1844 with a
platform supporting the
goals of Manifest Destiny.
Polk supported the
Manifest Destiny and the
expansion of the United
States from “Sea to
shining sea.”
Steps to War
American Version
 March 1846 – General
Taylor’s troops made
camp at the Rio Grande in
disputed territory
 Mexican forces crossed
the Rio Grande and
attacked group of 63 U.S.
soldiers
 11 Americans killed
Mexican Version
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April 1846 – Mexican
commander insisted U.S.
troops must leave area
and Taylor refused to
move
Then American army
provoke Mexican Army
into firing first
Steps to War
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May 11, 1846 – Polk addressed
Congress
He declared that “Mexico has shed
American blood upon the American
soil.”
Two days later Congress declared war
on Mexico
Support of the War
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For many Americans the war led to
greater national pride
Many people believed it would spread
republican/American values
Southerners want war because it will
expand slavery
Opposition to the War
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Northerners oppose it because of slavery
issue
Some think the conflict was unjustified
Illinois Congressman Abraham Lincoln wrote
the “Spot Resolutions” in 1848– asking Polk
to show the spot where American blood had
been shed on American soil
The Bear Flag Revolt
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June 1846
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War declared on Mexico
Americans in California declared Independence
from Mexico
John C. Fremont
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Leads revolt against Mexico to gain the territory of
California
Leaders raise the bear flag in defiance of Mexico
The Bear Flag Republic
The Revolt  June 14,
1845
John C. Frémont
Battle of San Gabriel
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Near Los Angeles
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United States Victory
U.S. Takes possession of California.
What the U.S. had once offered $25 Million
for, they now took by force.
Conquest of New Mexico
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Steven Kearny
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Takes New Mexico
Took Santa Fe without
bloodshed
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Brought American Rule to
New Mexico
Battle of Monterey
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Zachary Tayolor
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Future U.S.
President
Monterey
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Very bloody battle
The Bombardment of Vera Cruz
General Scott Enters Mexico City
US
victory—
September
1847
Conquest of Mexico City
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Mexico City
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Population Center
The attack was to convince Mexico of their
loss of the Northern Territories
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When Santa Anna loses, Polk offers him $1
Million to sign a peace treaty
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Santa Anna refuses
The U.S. defeats Mexico City
Legacies of Mexican-American War
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“Small war”—not many lives lost
Gained a ton of land (increased size of
US by 1/3)
Prepared military and soldiers for Civil
War
Led to Mexican resentment
Aroused issue of slavery which would
lead to Civil War
The Treaty of Guadalupe
Hidalgo (1848)
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Forced on Santa Anna and Mexico
Southern boundary of Texas set at the Rio Grande
U.S. gained:
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Present-day states of California, Nevada, and Utah
Most of Arizona and New Mexico
Parts of Colorado and Wyoming
U.S. agreed to pay $15 million to Mexico and pay
debts of Mexico to U.S. citizens