What was the idea US should extend Atlantic ocean to Pacific Ocean?

The idea of the U.S. extending from the Atlantic Ocean to the Pacific Ocean is known as Manifest Destiny, a 19th-century belief that American settlers were destined to expand across North America. This concept fueled westward expansion and justified territorial acquisitions, such as the Louisiana Purchase and the annexation of Texas. Proponents believed it was both a right and a duty to spread democracy and civilization. Manifest Destiny played a significant role in shaping U.S. policies and territorial boundaries during that era.