Which of the following wars occurred first?

The Civil War occurred first among the wars listed. It took place from 1861 to 1865 and was a pivotal conflict in American history, fighting primarily over the issues of slavery and states' rights.

In contrast, the Spanish-American War happened later, in 1898, and involved conflicts primarily over Cuba's fight for independence from Spain. World War I began much later, from 1914 to 1918, involving global alliances and significant changes in warfare. The Vietnam War also followed these events, with U.S. involvement escalating in the late 1950s and continuing through to 1975.

Understanding the sequence of these wars is essential for grasping the context of U.S. history and the evolution of national and international relations.