How the United States grew, in order. Each entry shows the lands added (or taken), why it mattered, and which content standard it belongs to. Use this page to picture westward expansion as a sequence — not just a list of names.
The starting line. After the Revolution, the United States was a thin strip of thirteen colonies hugging the Atlantic coast — bordered by British Canada to the north, Spanish Florida to the south, and the Mississippi River far to the west.
The Treaty of Paris ended the Revolution and gave the United States a huge stretch of land between the Appalachians and the Mississippi River. The U.S. instantly almost doubled in size before any westward expansion even began.
President Jefferson bought roughly 828,000 square miles from France for about $15 million — around 3 cents an acre. The deal doubled the size of the United States and gave Americans control of the Mississippi River and the port of New Orleans.
After the War of 1812, the U.S. and Britain agreed on a clean northern border at the 49th parallel from the Lake of the Woods to the Rocky Mountains. They also agreed to jointly occupy the Oregon Country for the time being.
Spain ceded Florida to the United States and gave up its claims to the Pacific Northwest in exchange for $5 million in damage claims. The deal also drew a clear southwestern boundary between the U.S. and New Spain.
The Indian Removal Act (1830) forced tens of thousands of Cherokee, Creek, Choctaw, Chickasaw, and Seminole people from their homelands in the Southeast onto land west of the Mississippi River. The forced march that followed became known as the Trail of Tears.
In the 1840s, thousands of American settlers loaded covered wagons and followed the 2,000-mile Oregon Trail from Missouri to the Willamette Valley. Drawn by free farmland and the idea of Manifest Destiny, they helped pull Oregon firmly into the American orbit.
After winning independence from Mexico in 1836, the Republic of Texas asked to join the United States. Congress finally agreed in 1845, making Texas the 28th state — and infuriating Mexico, which still considered Texas its own territory.
After years of joint occupation and the campaign cry of “54°40′ or Fight,” the U.S. and Britain peacefully split the Oregon Country at the 49th parallel — the same line used farther east. The American share later became Oregon, Washington, and Idaho.
The U.S. claimed the Rio Grande as the southern border of Texas; Mexico said the border was the Nueces River, much farther north. President Polk sent troops into the disputed strip, fighting broke out, and the Mexican-American War began.
The Treaty of Guadalupe Hidalgo ended the war and forced Mexico to give up roughly 525,000 square miles — about half of its land. The U.S. paid $15 million. The cession included present-day California, Nevada, Utah, and parts of Arizona, New Mexico, Colorado, and Wyoming.
The U.S. paid Mexico $10 million for a thin strip of land along the southern edges of present-day Arizona and New Mexico. The land was wanted for a southern transcontinental railroad route. This was the final piece needed to complete the lower 48 states.
The Union Pacific built west from Omaha, Nebraska while the Central Pacific built east from Sacramento, California. Their tracks met at Promontory Summit, Utah on May 10, 1869, finally linking the East Coast to the Pacific by rail.
Once you can recognize each acquisition on its own, try seeing them all at once. The blank map at the bottom is a quick self-quiz — cover the answers and label each region from memory.
