Mexican-American War
Causes of the War
Texas was annexed by the United States on
December 29, 1845. Many Mexicans were afraid
this was just the first step in the United States
taking over all of Mexico.
Texas and Mexico were still fighting over the
boundaries when the United States annexed Texas.
• Mexico claimed the Nueces River as the boundary.
• Texas and the United States claimed the Rio Grande as the
Causes of the War
Man U.S. citizens wanted to be repaid for damage
done to their businesses and property in Mexico.
U.S. leaders were angry when Mexico ordered all
U.S. settlers to leave the Mexican territory of
President James K. Polk sent John Slidell to
Mexico to try to buy New Mexico and California.
• Mexico officials refused to meet with him.
Fighting Starts
President Polk sent General Zachary Taylor to
the Rio Grande to protect the U.S. border.
General Taylor and 1,000 troops arrived at the
Rio Grande in March 1846.
• There was a Mexican camp on the other side of the river.
• General Taylor ordered his men to build a fort
along the river by present-day Brownsville.
The President and the General
President James K. Polk
General Zachary Taylor
Fighting Starts
In April the Mexican General sent a note to
General Taylor and ordered him to “return to the
east bank of the Nueces River”.
Taylor refused.
On April 25 a force of 1,600 Mexican cavalry
crossed the Rio Grande and attacked.
Most U.S. soldiers were captured, but 11 were
killed and 5 were wounded.
The next day General Taylor sent word to
Washington that the fighting had begun.
Call for War
When President Polk heard about this he went to
Congress and asked them to declare war on
Debate in the Congress
-“American blood has been spilt on American soil!”
-“American blood has been spilt on a Mexican corn field.”
–Abraham Lincoln
Congress declared war on May 13, 1846
Abraham Lincoln in 1846
More Fighting
Before news of the declaration of war more
fighting occurred.
May 8-9, 1846 – General Mariano Arista
attacked at Palo Alto and Resaca de la
Palma (both on north side of the Rio
The United States Army won both battles.
Texans in the War
When fighting broke out 6,000 Texans
volunteered to join the army.
Many Texans wanted the chance to fight their old
rival again – Antonio Lopez de Santa Anna.
Texas Governor James P. Henderson temporarily
left office to join and lead Texas forces.
Former Texas President Mirabeau B. Lamar
Texas Revolutionary, Juan Seguín, was forced to
join the Mexican army.
Texans in the War
James P. Henderson
Mirabeau B. Lamar
Texas Governor
2nd Texas President
Juan Seguín
Texas Revolutionary
Texas Rangers in the War
Several Rangers, including Rip Ford and John Coffee
Hays, joined the U.S. Army.
-They were scouts for the army.
Some Rangers caused problems
-They wouldn’t follow orders.
-They also attacked Mexican towns.
General Taylor threatened to throw all the Rangers in jail.
Many Mexican feared them.
-They called them Los Diablos Tejanos (“The Texas Devils”).
Texas Rangers in the War
Texas Rangers in the War
U.S. Victory
After winning battles in Texas, General
Taylor began an offensive – a major troop
advance – into northern Mexico.
U.S. forces won two major battles at
Monterrey and Buena Vista.
At Buena Vista Santa Anna was in
command of the Mexican forces and he
demanded a surrender from General Taylor.
U.S. Victory
Officer Thomas L. Crittenden simply replied,
“General Taylor never surrenders.”
After two days Santa Anna’s forces retreated.
New Battle Plan
General Winfield Scott began a new
strategy in the fall of 1846
Troops would land at Veracruz and march
west to attack Mexico City
President Polk liked his idea so much he
gave General Scott 9,000 of General
Taylor’s men
Plan in Action
March 1847 Scott’s troops landed near Veracruz
By mid-September they had captured Mexico City
Scott won the battles of Veracruz, Cerro Gordo,
Contreras/Padierna, Buena Vista, and Molino del
Rey, then assaulted the fort of Chapultepec which
surrendered on September 13, 1847.
Other U.S. forces had taken control of California
and parts of New Mexico
The Cost of War
Major fighting ended on September 14, 1847
when U.S. troops raised the American flag over
the National Palace in Mexico City
Of the 116,000 U.S. soldiers 13,000 died
– Many of those died from disease
More than 60 Texans died in battle and 270 died
from disease or accidents
The war with Mexico cost America $98 million
Treaty of Guadalupe Hidalgo
After the capture of
Mexico City U.S.
diplomat, Nicholas
Trist, met with Mexico’s
acting president in the
city of Guadalupe
Nicholas Trist – U.S. diplomat
Treaty of Guadalupe Hidalgo
Ended the Mexican War
Signed on February 2, 1848
Mexico recognized the annexation of Texas
Mexico recognized the Rio Grande as the
United States agreed to pay the $3.25
million in claims of the U.S. Citizens had
against Mexico
Treaty of Guadalupe Hidalgo
As part of the Treaty of Guadalupe Hidalgo
Mexico agreed to cede, or give up, some
529,000 square miles of its northern land to
the U.S. for $15 million
This is known as the Mexican Cession
Problems in America
After the Mexican War debates over slavery
Pro-slavery wanted to allow slavery in the
new territories
Anti-slavery didn’t want to allow slavery in
the new territories
Texas and New Mexico started to fight over
Compromise of 1850
In 1850 Senator Henry Clay came up with a plan
The federal government would pay Texas $10
million dollars to give up its claim to New Mexico
– The state needed the money to pay bills left over from
the Republic of Texas so they agreed
Also the plan said that no territories above the 30th
parallel could be a slave state
Compromise of 1850