Lesson 1: The Thirst for New Lands

Lesson Focus

Explore 'manifest destiny,' the belief that America was destined to expand from the Atlantic to the Pacific. This lesson examines the powerful forces that drove the nation's westward push and territorial acquisitions during the 1840s.

People to Know

Daniel Webster, Lord Ashburton

Learning Objectives

• Explain why Americans were driven to expand their territory all the way to the Pacific Ocean.
• Describe how the U.S. negotiated with Great Britain to settle disputes over land, like the territory of Maine.

In the 1840s, many Americans believed their nation had a divine mission to expand across the continent. New York editor John L. O'Sullivan named this idea manifest destiny.

He argued it was America's right to spread its experiment in liberty. This powerful belief, combined with a restless pioneer spirit and a desire for new land, fueled a massive migration westward and justified taking over lands claimed by others.

A major cause for westward migration was the mistaken belief that the Great Plains, or “Great American Desert,” was unfarmable land best left to Indian nations.

To find fertile, forested lands, settlers had to cross the Rockies to the Pacific Coast. Additionally, eastern merchants pushed for expansion, seeking valuable Pacific harbors like San Francisco for trade with Asia. This led to a huge migration to Oregon and California.

The push for manifest destiny created conflict with other peoples who already claimed western lands.

The United States faced three main rivals: Native American groups like the Arapaho and Comanche, who were divided and at a technological disadvantage; a politically unstable Mexico; and the powerful British Empire. Fortunately for the U.S., its rivals were either too weak or unwilling to fight, creating a 'power vacuum' that aided American expansion.

Tensions with Britain flared over the border of Maine. In 1838, Britain began planning a road through the disputed Aroostook Valley to connect its Canadian territories.

In 1839, American settlers clashed with British workers, starting the Aroostook War. Though mostly a fist-fight, both sides called up militias, bringing the two nations to the brink of a larger war. Note that this crisis highlighted the need for a diplomatic solution.

Despite rising tensions, both the U.S. and Great Britain depended heavily on trade with each other, creating a strong reason for peace.

In 1842, U.S. Secretary of State Daniel Webster met with Britain's Lord Ashburton to negotiate. They agreed to the Webster-Ashburton Treaty, which fairly divided the disputed land. This treaty gave the U.S. the fertile Aroostook Valley, secured Britain's road, and successfully prevented war between the two nations.