Manifest Destiny: This is a belief that was prevalent during the 19th century among American settlers that they were destined by God to expand their territory across North America.
Oregon Trail: A historic east-west large wheeled wagon route connecting the Missouri River to valleys in Oregon. It was one of the main overland migration routes on which pioneers traveled across North America in wagons.
Louisiana Purchase: The acquisition of French Louisiana by the United States from France in 1803. This nearly doubled the size of U.S territory, paving way for further westward expansion.