Chapter 9 Section 3

Do Now!
Wilmot Proviso: Banned slavery in any lands
won from Mexico.
Treaty of Guadalupe Hidalgo: Added 1.2
million square miles of territory to the United
California Gold Rush: A mass migration of
people seeking their fortunes.
EQ: What were the effects of the
Mexican-American War and
California Gold Rush?
The students will be able to recall and
evaluate the concepts of Manifest
Destiny and United States society
Ch 9 Sec 3: Effects of Territorial
• In 1848, Mexico and the U.S. signed the
Treaty of Guadalupe Hidalgo. Mexico gave up
the northern third of their country. In 1853,
the U.S. bought more territory in southern
Arizona and New Mexico from Mexico as part
of the Gadsden Purchase for $18 million. The
new lands comprised present-day New
Mexico, California, Nevada, Utah, Arizona, and
half of Colorado.
• The Mexican-American War had many effects.
The new territories made the fight over
slavery even more heated. Congress divided
into pro-slavery and anti-slavery groups after
the Wilmot Proviso was proposed, a bill that
would have banned slavery in the new
• In 1848, gold was discovered in California. The
discovery set off the California Gold Rush. Tens
of thousands of people called forty-niners
moved west. Some forty-niners came from
South America. Another 25,000 laborers came
from China. In just five years, California’s
population jumped by more than 200,000
• Most of these miners had a difficult, violent
life. They worked hard, earned little, and
suffered from disease and poor living
• At first, the miners used cheap metal pans to
find gold in rivers and streams. This process
was known as placer mining. Over time,
however, better equipment was used.
Hydraulic mining employed jets of water to
erode gravel hills.
• The rapid settlement of California had many
effects. Native Americans were killed and
terrorized by the thousands. Many Mexican
Americans lost their land and their rights.
• California also caused a problem when it
applied for statehood. At that time, the
number of slave and free states in the nation
was equal. If California became a free state, it
would tip the balance. This would upset proslavery states. Northern and southern
congressmen debated slavery yet again.
• How did the Mexican-American War serve to
heighten tensions over slavery?