Which concept exemplifies the belief in American expansion during the 19th century?

The belief in American expansion during the 19th century is best exemplified by Manifest Destiny. This concept was rooted in the idea that the United States was destined to expand across the North American continent, from the Atlantic to the Pacific Ocean. Advocates believed that this expansion was not only a right but also a moral obligation, as they viewed it as a way to spread democracy, civilization, and culture. The phrase "Manifest Destiny" was popularized in the 1840s and was used to justify the United States’ territorial acquisitions, such as the annexation of Texas, the Oregon Trail migration, and the acquisition of California following the Mexican-American War.

The concept of Manifest Destiny fueled a sense of nationalism and led to significant political and social movements. It was intertwined with notions of racial superiority, as many believed that Anglo-Saxon Americans were more suited to govern the vast lands. This widespread belief had profound effects on U.S. policy and interactions with Native American populations and other nations.

In contrast, isolationism refers to a foreign policy stance of non-involvement in international affairs, which does not support the idea of expansion. Industrialization pertains to the economic transformation into an industrial economy, which, while significant in the 19th century,