Sea Power and the Frontier: The Debate over American Expansion

By the 1890s many Americans debated whether the United States should acquire overseas colonies, and supporters drew on several arguments. Alfred Thayer Mahan's 1890 book argued that a great nation needed a strong navy, coaling stations and a canal between the oceans.

The historian Frederick Jackson Turner declared in 1893 that the American frontier had closed, which some took to mean the nation needed new outlets for its energies. Business leaders sought markets in Asia and Latin America, especially during the economic depression that began in 1893, and some Protestant writers spoke of a mission to spread Christianity and civilization.

Opponents formed the Anti-Imperialist League in 1898, whose members included Mark Twain and the industrialist Andrew Carnegie. They argued that ruling other peoples without their consent violated the Declaration of Independence, while some opponents also held racist fears of incorporating non-white populations. The debate shows that empire divided Americans deeply.