This article uses the first issue of the American Journal of International Law, one hundred years after its creation in 1907, to analyse the state of American international legal thought following the acquisition of Pacific and Caribbean island territories in the Spanish–American War and the creation of a new international identity. Traditionally, the American Society of International Law (of which the journal was the organ) has been placed in the context of the US peace movement. However, both the society and the journal were led by individuals occupying major positions in the administration of Theodore Roosevelt and earlier administrations, including the sitting and a former secretary of war. The society and its journal were vehicles of the US foreign policy establishment. Despite a mixture of imperialists and anti-imperialists, a cultural coherence is discernable in the journal's pages. In essence, the journal can be placed within what the article calls the genteel tradition of US international law, involving an effort at educating the public away from over-excitement, adopting science in the newly professionalized administrative state, and advocating an arbitrational model of legal ordering to promote international peace.