Which event is commonly associated with the start of U.S. imperialism in the late 19th century?

The Spanish-American War is widely recognized as a pivotal event that marked the beginning of U.S. imperialism in the late 19th century. This conflict, which occurred in 1898, resulted in the United States emerging as a global power with significant territorial acquisitions. The war was fought between the United States and Spain, primarily over issues of Cuban independence, but it led to the U.S. gaining control over territories such as Puerto Rico, Guam, and the Philippines. This expansion beyond the continental U.S. demonstrated a shift in American foreign policy towards a more imperialistic approach, characterized by the desire to exert influence and control over distant territories.

In contrast, the annexation of Alaska was a purchase aimed at expanding U.S. territory but did not signify a broader imperialist agenda. The Louisiana Purchase happened much earlier, in 1803, and involved the acquisition of land from France rather than overseas imperialism. The signing of the Treaty of Paris, while significant in ending the American Revolutionary War and acknowledging U.S. independence, occurred in 1783 and does not relate to the late 19th-century context of imperialism. Therefore, the Spanish-American War is integral to understanding the transition of the United States into an era of imperialism