Legalist Empire explores the intimate connections between international law and empire in the United States from 1898 to 1919. Though many histories treat Woodrow Wilsons plans for the League of Nations as the beginning of Americas substantive engagement with international law, this book demonstrates the broad influence of legal concepts and expertise in the years before World War I. It follows such lawyers as Elihu Root, John Bassett Moore, James Brown Scott, and Robert Lansing as they created an American profession of international law, promoted the creation of international courts, represented corporations with business overseas, and served as high-ranking policymakers in Washington. A widespread belief in the inevitable progress of civilization simultaneously justified American empire and underwrote the claim that international adjudication could bring world peace. Legalist Empire shows how international lawyers justified the conquest of the Philippines, the taking of Panama, and interventions throughout the Caribbean, and also explains why the law of neutrality helped lead the United States into World War I. The book also offers a new history of the origins of the American international law profession. Research in the papers and publications of lawyers and their organizations shows how political, ideological, and cultural assumptions shaped the emerging profession. A conclusion tracing developments to the present further emphasizes that rather than being antagonists, empire and the international rule of law have frequently reinforced each other in American history.