What concept describes the expansion of the U.S. territory across the North American continent?

The concept that describes the expansion of U.S. territory across the North American continent is Manifest Destiny. This idea emerged in the 19th century and encapsulated the belief that it was the divine right and destiny of the United States to expand its territory, spreading its values and civilization across the continent. This belief justified the westward expansion and was used to rationalize various actions, including the annexation of lands and displacement of Native American populations. Manifest Destiny played a crucial role in national policy and popular sentiment, influencing events such as the Louisiana Purchase, the Oregon Trail migration, and the Mexican-American War.

The other terms do not accurately capture this specific historical context. Territorialism could imply a general sense of land occupation but lacks the ideological and nationalistic fervor associated with Manifest Destiny. Colonialism typically refers to the control of foreign territories and their peoples, rather than the continental expansion of an existing nation-state. Imperialism is a broader term that signifies the policy of extending a country's power and influence through various means, including military force, but it does not encapsulate the specific historical narrative of the U.S. manifesting its destiny across North America.