The Mexican War began in 1846 as a result of a border dispute between the United States and Mexico and America's desire to extend its territory westward in line with Manifest Destiny. President Polk provoked Mexico into conflict so he could justify war, and the U.S. quickly gained control of New Mexico and California. The 1848 Treaty of Guadalupe Hidalgo ended the war, with Mexico ceding those territories to the U.S. in the Mexican Cession in exchange for $15 million.

1. The Mexican War

2. • In the early 1800s the vast
region between the Texas
and California Territories
was called New Mexico
- It included present-
day New Mexico, Arizona,
Nevada, Utah, and parts of
Colorado and Wyoming
• In 1821 New Mexico became
part of Mexico when it
became independent from
Spain

3. • The Mexican government
welcomed Americans into
New Mexico, hoping that
trade would boost the
economy
• William Becknell was the first
American to reach Santa Fe,
NM’s capital
• He took a route from
Independence, Missouri to
Santa Fe, NM, which became
known as the Santa Fe Trail,
an important trade route

4. • As Americans began settling in NM, they wanted the U.S. to acquire the region
as a state
• They also wanted the Mexican territory of California, which would give access
to the Pacific Ocean
• Spanish explorers and missionaries had settled in California in the 1700s

5. • In the 1760s, a Catholic priest named Fr. Junipero Serra began building a
string of missions from San Diego to Sonoma
• The Spanish had hoped to convert the Native Americans to Christianity. By
1820, there were 21 missions in California

6. FYI: Junipero Serra
was canonized a
saint in 2015 by
Pope Francis

7. • California became a state
in the Mexican nation
when Mexico gained
independence from Spain
in 1821
• In 1833 the Mexican gov’t
abolished the missions
• Mexican settlers bought
the land and built huge
properties, where the
rancheros (or ranch
owners) treated the
Native Americans almost
like slaves

8. • At first, Mexican authorities welcomed American traders and merchants to
California, and in the 1840s, American families started to settle there.
• President Polk offered to buy both California and New Mexico, but the
Mexican gov’t refused
• Polk was determined to fulfill the U.S.’s Manifest Destiny; he was ready to go
to war to acquire both regions for the Union
• He decided to provoke Mexico into taking military action first, so he could
justify a war to Congress

10. • At that time, the U.S. also had a dispute with Mexico over the Texas-Mexico
border. The U.S. said the Rio Grande formed the border; Mexico claimed it
was the Nueces River

11. • Polk sent an agent to Mexico to propose a deal regarding Texas, New Mexico,
and the Texas border
• The Mexican gov’t refused the offer, and said that it intended to reclaim Texas
• Polk ordered General Zachary Taylor to build a fort and march across the land
between the Nueces River and the Rio Grande
• In April 1846 Mexican forces attacked a group of Taylor’s soldiers
• The U.S. Congress declared war against Mexico

12. • The American people were divided
– most Democrats supported the
war, while most Whigs opposed it
• Illinois Congressman Abraham
Lincoln opposed the war, and felt
that Polk had no grounds for
blaming the war on Mexico

13. FYI:
• Photography was commercially
introduced in 1839
• John Quincy Adams was the first
president to have his photograph
taken, in 1843, 14 years after he left
office
• James K. Polk was the first to be
photographed while in office; Polk was
also the first president to be extensively
photographed during his presidency

14. President Polk was photographed while
in office on February 14, 1849. This
image is the first surviving photograph
taken of a president while in office.

15. • By 1847, Taylor’s army secured the
Texas border
• In 1846, General Stephen Watts
Kearny led troops into New Mexico;
the Mexican gov’t fled and the
Americans captured Santa Fe
• In June, a group of Americans seized
Sonoma and proclaimed the
Independent Republic of California
• They called it the Bear Flag Republic
(can you guess why?)

16. THEN
NOW

17. • In July 1846, the U.S. navy captured two California ports, and by January 1847,
California was fully under the control of the U. S.
• By September of 1847, Americans had taken Mexico City; the Mexican gov’t
surrendered

18. • The Treaty of Guadalupe Hidalgo was signed in February 1848
- Mexico gave up all claims to Texas and agreed to the Rio Grande as the
border between Texas and Mexico
- In the Mexican Cession, Mexico gave California and New Mexico to the
U.S.
- The U.S. gave Mexico $15 million

19. • In 1853 the U.S. paid
$10 million in the
Gadsden Purchase,
land that was part of
the southern edge of
Arizona and New
Mexico

20. • With the Gadsden Purchase, the continental U.S. reached its present
size, and was closer to fulfilling its Manifest Destiny