The term "Manifest Destiny" signifies a 19th-century belief that American expansion across the continent was both justifiable and predetermined. This ideology was rooted in the belief that the United States was destined to spread democracy and capitalism across North America, often at the expense of Indigenous peoples and other nations. It fueled westward expansion, leading to significant territorial acquisitions such as the Louisiana Purchase and the annexation of Texas. Manifest Destiny justified the displacement of Native Americans and contributed to tensions with Mexico, culminating in the Mexican-American War. Its legacy remains controversial, impacting discussions of American exceptionalism and territorial expansion.