The United States and
Mexico at War
Chapter 12
The 28th State
• Mexico still refused to accept the
Treaties of Velasco
• The United States accepted
Texas’s southern border as the
Rio Grande
• Mexico still claimed all of Texas,
with the border of Texas and
Mexico as the Nueces River
Manifest Destiny
• The U.S. ultimately wanted to gain control of
California and all the lands between Texas and
the Pacific coast
The Threat of War
• When Texas was annexed Mexico threatened war
• President Polk sent John Slidell to Mexico
– U.S. residents filed claims against Mexico for damage to their
property
– Slidell offered that the U.S. would pay for these damages if
Mexico would recognize Texas as part of the U.S. and transfer
California and all the land between Texas and California to the
U.S.
– This offened Mexican officials
• Some U.S. citizens did not want the territories controlled by
Mexico-they feared the U.S. wanted this land, and Texas, in order to
expand slavery
Fighting Breaks Out
*The U.S. placed troops, under General Zachary Taylor,
along the Nueces River and Mexico placed troops, under
General Mariano Arista, along the Rio Grande
*When Mexico refused to discuss matters with Slidell U.S.
troops moved to the Rio Grande
*Fighting began in the disputed territory just north of the
Rio Grande and south of the Nueces River
*Both General Taylor and General Arista sent messages to
their governments claiming that they had been fired upon
on their own nations soil
The War with Mexico
* General Arista’a army moved north toward the U.S. troops
-The two groups battled at Palo Alto and Resaca de la Palma,
with the U.S. claiming victory at both location
* The U.S. declares war with Mexico on May 13, 1846, at President
James K. Polk’s urging
* After a fierce battle in Mexico City the U.S. forces occupy the city
* Many Texans eagerly took part in the battle as a way to “Remember
the Alamo”, and to settle arguments over the men of the Mier
expedition who were put in prison
* The Texas Rangers played a big part in the war, scouting for the
U.S. army
The Treaty of Guadalupe Hidalgo
•The treaty was signed on February 2, 1848
•Mexico agreed that Texas was now party of the U.S.
•Mexico surrendered all land between Texas and the
Pacific Ocean; this transfer of land was known as the
Mexican Cession, and included California, and all or part
of the future states of New Mexico, Arizona, Nevada,
Wyoming, Utah, and Colorado
•In return the United States paid Mexico $15 million
•The U.S. also took over claims by U.S. citizens against
Mexico
Texas-New Mexico Dispute
* The Treaty of Guadalupe Hildago established the Rio
Grande as Texas’s southern border-but there was dispute
of Texas’s western border
* The Rio Grande continued through El Paso, through
central New Mexico, to its source in the San Juan
Mountains in Colorado
* This would place almost half of New Mexico, including its
largest city and capital, Santa Fe in Texas
* New Mexicans had close ties to Mexico and were still
angry that Mirabeau Lamar had tired to control the area
Texas’s Efforts to Gain Control Over
New Mexico
•To strengthen Texas’s claims to New Mexico the state
legislature created new counties in the disputed area
•Texas Governor, George Thomas Wood, sent Texas
Ranger Robert S. Neighbors to organize the counties
•Neighbors was only able to persuade El Paso to agree
that they were part of Texas
Disagreements over Slavery and
Territories
•When Zachary Taylor won the presidency of the U.S. in 1848,
he agreed to support the admission of California to the Union
as a free state (or a state that did not permit slavery)
• However California as a free state would upset the balance of
free and slave states
• For that reason pro-slavery states did not want California to
be admitted
• The residents of Utah and New Mexico wanted their territories
to be admitted to the Union
•How far Texas extended west added to the controversy over
slavery-because it was a slave state many people wanted its
borders to be limited
Disagreements over Slavery and
Territories
•President Taylor demanded that California be admitted
right away-he argued that the residents of California were
struggling with problems after the Gold Rush of 1848 and
were in need of a state government for stability
•Many representatives in Congress wanted to wait until
the issue of slavery in all the territories had been settled
•Southern members of Congress also wanted a federal
law to provide help finding runaway slaves-this law
became known as the Fugitive Slave Law
Disagreements over Slavery and
Territories
•Senator Henry Clay of Kentucky offered a compromise
•Immediate admission of California as a free state
•The organization of the New Mexico and Utah
territories-and the residents of these territories would
decide the question of slavery on their own
•The abolition of slave trade in Washington D.C.
•The enactment of the Fugitive Slave Law
•Texas would give up about 40% of its western lands in
exchange for $10 million
The Compromise of 1850
•President Taylor demanded the Congress admit
California to the Union before he would respond to Clay’s
proposals
•The situation was resolved when President Taylor died in
1850 and Vice-President Millard Fillmore assumed the
presidency
•Congress passed the Compromise of 1850: California
became a state, New Mexico and Utah became territories,
the slave trade in Washington D.C. ended and the south
received its Fugitive Slave Law
The Texas and New Mexico Act of
September 9, 1850
•Texas gave up some of its land to the north and west
•In return Texas received $10 million
•This act created Texas’s present-day border
•While some Texans were not in favor of surrendering so
much territory, others realized that the state needed the
money more than it needed the land
The Compromise of 1850