The United States Gains Western Territory
The United States expanded westward through purchases, treaties, and military conquest, nearly tripling in size between 1803 and 1848. The Louisiana Purchase from France doubled the nation overnight, while a treaty with Britain resolved the Oregon Country border. Texas annexation and victory in the Mexican-American War added vast southwestern lands including California. This Grade 5 history topic from Social Studies Alive! Americas Past traces how the U.S. built its continental territory and the different methods used. Understanding territorial expansion is essential for grasping both Manifest Destiny and the political and human costs of growth, including the displacement of Mexican citizens and Native peoples.
Key Concepts
The United States grew larger by acquiring land in several ways. Sometimes, the U.S. used money to purchase huge areas, like the Louisiana Territory . Other times, it made a treaty, or formal agreement, with another country to set new borders, like it did for the Oregon Country .
The country also grew through conflict. The U.S. annexed Texas, which means it added the territory to the country. This led to a war with Mexico. After the U.S. won, it took a vast amount of land that had belonged to Mexico.
Common Questions
How did the United States gain western territory?
The U.S. gained western territory through several means: purchasing the Louisiana Territory from France in 1803, negotiating the Oregon Country border with Britain, annexing Texas in 1845, and winning the Mexican Cession after the Mexican-American War in 1848.
What was the Louisiana Purchase?
The Louisiana Purchase was a land deal in 1803 in which the United States bought approximately 828,000 square miles of territory from France for about 15 million dollars. This doubled the size of the United States overnight.
What was the Mexican Cession?
The Mexican Cession was the territory the United States gained from Mexico after winning the Mexican-American War in 1848. It included present-day California, Nevada, Utah, Arizona, New Mexico, Colorado, and Wyoming.
When do 5th graders learn about U.S. territorial expansion?
Fifth graders study U.S. territorial expansion in Grade 5 social studies as part of Chapter 5 of Social Studies Alive! Americas Past, which covers Manifest Destiny and how the country grew.
What is Manifest Destiny?
Manifest Destiny was the belief, popular in 19th-century America, that the United States was destined to expand from the Atlantic to the Pacific Ocean. It was used to justify territorial acquisitions and the displacement of Native peoples and Mexican citizens.
How did Texas become part of the United States?
Texas declared independence from Mexico in 1836 and became the Republic of Texas. In 1845, the U.S. Congress voted to annex Texas, making it a state. This action helped trigger the Mexican-American War.