Between 1815 and 1900 the nation fought wars that protected its independence, expanded its continental frontiers, and subdued Native Americans; it survived a bloody Civil War; and it won a "Splendid Little War" against Spain that created an empire that included Cuba and the Philippines. These wars, especially the Civil War and Spanish-American war, occurred while the United States was becoming an urban, industrial, and multicultural nation. By the end of the nineteenth century, industry and technology, such as steam-driven ships and the machine gun, had transformed warfare. To understand the impact of war upon American society and culture requires an understanding of the underlying changes, such as urbanization, that were modernizing the nation.

During the nineteenth century, cities in the United States grew significantly. Factors such as large-scale immigration and rapid industrialization contributed to this process of urbanization. By the end of the century, instead of moving to frontier...