Timeline of events occurring during the westward expansion
1803: Louisiana Purchase - President Thomas Jefferson buys the Louisiana Territory from France for $15 million. This doubles the size of the United States and provides a large area to the west of the country for expansion.
1805: Lewis and Clark reach the Pacific Ocean - Explorers Lewis and Clark map out areas of the Louisiana Purchase and eventually reach the Pacific Ocean.
1836: Battle of the Alamo - Mexican troops attack the Alamo Mission killing all but two Texans. This spurs the Texans on in the Texas Revolution.
1841: Oregon Trail - People begin to travel west in wagon trains on the Oregon Trail. Around 300,000 people would take the trail over the next 20 years.
1845: Manifest Destiny - Journalist John O'Sullivan first uses the term "Manifest Destiny" to describe the westward expansion of the United States.
1845: Texas becomes a U.S. State - The United States officially claims Texas as a state, eventually leading to the Mexican-American War.
1846: Brigham Young leads 5,000 Mormons to Utah - After experiencing religious persecution, the Mormons move to Salt Lake City, Utah. Also known as the Mormon Trail.
1846-1848: The Mexican-American War - A war fought over the rights to Texas. After the war, the United States paid Mexico $15 million for land that would later become California, Texas, Arizona, Nevada, Utah, and parts of several other states.
1846: Oregon Treaty - England signs the Oregon Treaty handing over the Oregon Territory to the United States.
1848: Gold Rush begins - James Marshall discovers gold at Sutter's Mill. Soon word is out and people rush to California to strike it rich.
1849: Around 90,000 "Forty-niners" move to California to find gold.
1872: Yellowstone National Park is dedicated as the nation's first national park by President Ulysses S. Grant.
1890: The U.S. Government announces that the Western lands have been explored.