This four-volume collection brings together a diverse array of primary sources that help contextualise the impacts of American imperialism across the long nineteenth century. These fascinating volumes chart the motivations for, and reactions to, the growth of the United States from the American Revolution to the end of the First World War. Accompanied by extensive editorial commentary, the collection provides a valuable resource for those seeking to explore the causes, course, and consequences of US imperialism from 1775 to 1919.