In this Grade 5 Pengi Social Studies lesson from Chapter 8: Westward Expansion, students explore the causes of the Mexican-American War and how the Treaty of Guadalupe Hidalgo shaped the modern boundaries of the American Southwest. The lesson also covers the 1849 Gold Rush and California's admission to the Union in 1850, showing how these events transformed the nation's geography and growth.
Section 1
War with Mexico and the Treaty of Guadalupe Hidalgo
The desire for land led to conflict. After the U.S. annexed Texas, a dispute over the border sparked the Mexican-American War in 1846.
The U.S. won, and the war ended with the Treaty of Guadalupe Hidalgo.
In this treaty, Mexico was forced to give up half its territory—the Mexican Cession—which included present-day California, Nevada, Utah, Arizona, and parts of New Mexico. The U.S. map now stretched coast to coast.
Section 2
The California Gold Rush
Just as the war ended, gold was discovered at Sutter’s Mill in California. This sparked the Gold Rush of 1849.
"Forty-niners" from all over the world rushed to California hoping to get rich. While few found gold, the population boomed.
This rapid growth allowed California to skip being a territory and become the 31st state in 1850, changing the West forever.
Expand to review the lesson summary and core properties.
Section 1
War with Mexico and the Treaty of Guadalupe Hidalgo
The desire for land led to conflict. After the U.S. annexed Texas, a dispute over the border sparked the Mexican-American War in 1846.
The U.S. won, and the war ended with the Treaty of Guadalupe Hidalgo.
In this treaty, Mexico was forced to give up half its territory—the Mexican Cession—which included present-day California, Nevada, Utah, Arizona, and parts of New Mexico. The U.S. map now stretched coast to coast.
Section 2
The California Gold Rush
Just as the war ended, gold was discovered at Sutter’s Mill in California. This sparked the Gold Rush of 1849.
"Forty-niners" from all over the world rushed to California hoping to get rich. While few found gold, the population boomed.
This rapid growth allowed California to skip being a territory and become the 31st state in 1850, changing the West forever.