What’s Going On?
The Mexican American War
1846-1848
Mr. Polk’s War
Fifty-Four Forty or Fight
• Polk believes “Fifty- Four
Forty or Fight”
– U.S. should control all of
Oregon below the line of 54’
40’ north latitude
• Americans didn’t want to
fight, neither did the British
– British were fighting the Irish
Fifty-Four Forty or Fight
• Negotiated The
Oregon Treaty 1846
– U.S. Receives all of
Oregon South of 49’
– The British get
navigation rights on
the Columbia River
Adding Texas add to notes
• December 29, 1845
– Texas became the 28th
state in the Union
• Greatly ticked off Mexico
– Withdrew their
ambassador from
Washington
– War is inevitable
Tensions With Mexico
• U.S & Mexico are arguing over where the
border of Texas should be
– U.S.  Rio Grande
– Mexico  Nueces River
• Polk than sent an envoy to Mexico to try
to purchase the California, New Mexico &
resolve border issue
– John Slidell
– Mexican president refused to meet with him
Tensions With Mexico
• Polk “Make them come to us”
– Went to the Rio Grande, blockade the
river
– Led by Zachary Taylor
– Looks like an invasion of its territory
• Polk wants Mexicans to fire the first
shots
– Mexico would look like the aggressor
– Win support for the war in the US
To go to war, or not to?
• Southerners
– Good idea
– Extend slavery
– Increase southern power in
Congress
• Northerners
– Not a good idea
– Plot to expand slavery
– Ensure Southern domination of the
Union
To go to war, or not to?
• May 9th, 1846 news
broke that the Mexicans
had attacked Taylor’s
troops
– Polk declared War
– 9 U.S. Soldiers are killed
– “American blood has
been shed on American
Soil”
Tensions With Mexico
• Questioning the truthfulness of Polk’s claims
– Abraham Lincoln “ whether our citizens, whose
blood was shed, as in his message declared, were or
were not, at the time, armed officers and soldiers,
sent into that settlement by the military order of the
President?”
– Wanted a “Spot Resolution” certify the spot where
the skirmish occurred
• “Mr. Polk’s War”
War in New Mexico
• Polk ordered Colonel Stephen Kearny to march
from Kansas to Santa Fe, New Mexico
– “The Long Marcher”  800 miles
• Met in Santa Fe by a group of New Mexican
soldiers that wanted to be part of the U.S.
• New Mexico fell to the U.S. without a shot being
fired
– Heads to Southern California
The Republic of California
• 1800’s Spanish settlers had set up
many missions in along California coast
– Mexican government took control of
missions
• 1830’s about 12,000 Mexican settlers
had migrated to California
• Small number of Americans lived there
– 500
The Republic of California
• Polk offered to buy California
– Mexicans found it offensive
• Group of American settlers seized the town of
Sonoma in June 1846
– Declared their Independence from Mexico
– Republic of California
• Kearny arrived from New Mexico to help out
settlers, also Navy arrived
– Mexicans clearly out numbered gave up
The War in Mexico
• American invasion of Mexico
lasted about a year
– Captain Robert E. Lee, Captain
Ulysses S. Grant, General
Zachary Taylor
– General Winfield Scott
• “Old Fuss and Feathers”
• Successful victories in Mexico
The War in Mexico
• Polk scheming to try to end
the war
– Wants to help Santa Anna
sneak back into Mexico (been
in exile), Santa Anna would end
the war and fix border dispute
– Santa Anna returns to Mexico,
takes command of the army,
attacks Taylor’s troops
The War in Mexico
• However, Taylor’s
troops too strong
pushed Santa Anna
back
• At the same time,
Scott’s troops captured
Veracruz
– Moved on to capital,
Mexico City and won
America Gains The Spoils of War
• Mexico lost more than half of
its land and at least 25,000 lives
• American lost 13,000 lives but
territory grew by 1/3
• Treaty of Guadalupe Hidalgo
– February 2, 1848
– Rio Grande border for Texas
– U.S. Pays $15 million for New
Mexico & California
American Gains the Spoils of War
• 5 Years later, President
Pierce authorized the
purchase of additional land
from Mexico
• Gadsden Purchase
– The 1853 purchase by the
United States of land from
Mexico, establishing the
present U.S.-Mexico
boundary
Election of 1848
• Democrats run Lewis Cass
– Hesitant about the extension of slavery into new
territories
• Free- Soil Party runs Martin Van Buren
– Supported a congressional prohibition on the
extension of slavery in territories
• Whigs run Zachary Taylor
– War Hero
The California Gold Rush
• January 1848 James Marshall found
gold in the Sierra Nevada's in California
• People left in droves to pan for gold
– Left their houses, jobs, responsibilities
• 1848- 400 people v. 1850- 44,000
people
• Forty-Niners
– One of the people who migrated to
California in search of riches after gold was
discovered there in 1848
The California Gold Rush
• By 1849 California’s
population exceeded 100,000
– Chinese were the largest group
to come from overseas
– Free blacks also came  A lot
struck it rich
– Mexican population increased
as well