Which US foreign policy led to US expansion in the early 19th century?

The US foreign policy that led to expansion in the early 19th century is primarily the Monroe Doctrine. Announced in 1823 by President James Monroe, this doctrine asserted that the Western Hemisphere was under the influence of the United States and that European powers should not interfere in the affairs of the Americas. This policy aimed to prevent further European colonization and influence in the region, effectively establishing the U.S. as a dominant power in the Western Hemisphere, which laid the groundwork for future expansion.

• Seward’s Folly refers to the purchase of Alaska in 1867, which was significant but occurred later in the century.
• The Spanish-American War in 1898 marked a later stage of imperialism.
• The Roosevelt Corollary was an addition to the Monroe Doctrine articulated in 1904, addressing intervention in Latin America, but it is not part of the early 19th century expansion.

Therefore, the best answer is the Monroe Doctrine.