International organizations began to appear during the nineteenth century in the predominantly European state system. A considerable number of separate and limited-purpose agencies had accumulated by the outbreak of World War I. The organization-creating tendency of this period was stimulated primarily by the interdependencies engendered by the Industrial Revolution. New forms of production and new methods of transport and communication created problems and opportunities that necessitated more elaborate and systematic responses than those traditionally associated with bilateral diplomacy. International organization was an outgrowth of the multilateral consultation that came into vogue. It was a short step, and sometimes an almost imperceptible one, from convening a meeting of the several or many states whose interests were involved in a given problem and whose cooperation was essential to solving it, to establishing permanent machinery for collecting information, preparing studies and proposals, arranging recurrent consultations, and administering schemes agreed upon by the participating states.
The nineteenth-century concern with the challenge of developing rational multilateral responses to the changes wrought by steam and electricity in the economic and social spheres did not exclude concern with either the perennial or the newly developing problems of the "higher" sphere of international relations: war and peace, politics and security, law and order. Indeed it was clear that changes in the former spheres contributed to difficulties in the latter, and it was hoped that organized collaboration in the first might contribute to improvement in the second. Awareness of the increasing complexity of international politics, anxiety about the problems of preventing and limiting war, concern about the orderly balancing of stability and change, and hope for the strengthening of international law combined to inspire the ideal of applying international organization to the politico-legal realm.
The effort to do this at the end of the Napoleonic wars had yielded meager results, but the idea of giving firm institutional shape to the Concert of Europe persisted and was supplemented during the nineteenth century by the ideal of developing judicial means for the resolution of international disputes. It remained for the Hague Conferences of 1899 and 1907 to stimulate the hope, and for World War I to demonstrate the necessity, of extending the concept of international organization into the "higher" sphere of international relations. The League of Nations embodied that extension, represented an effort to provide a central focus for the varied organizational activities that had emerged in the preceding century, and accelerated the growth of the organizing process among states. The collapse of the League and the outbreak of World War II gave rise to the establishment of the United Nations and a network of affiliated organizations. It also gave impetus to the institution-building disposition of statesmen, not least on the European continent, that has produced scores of agencies of almost every conceivable size and concern. If the nineteenth century was the period of the beginning of the movement toward international organization, the twentieth century has been the era of its multiplication. In the post–Cold War world the landscape is dotted with international agencies: global and regional, single-purpose and multipurpose, technical and political, regulatory and promotional, consultative and operational, modest and ambitious. And the habit of creating new ones and maintaining old ones remains well established among statesmen. By any test of quantity and variety, international organization has become a major phenomenon in international politics.
The beginning of the trend toward international organization in the nineteenth century and the proliferation of that trend in the next substantially involved the United States. The well-known isolationist tradition of the United States and the fact that it rejected membership in the League of Nations but joined the United Nations at its creation should not be taken as evidence that America is a latecomer to international organization. On the contrary, American participation in the nineteenth-century organizing process was at least as active as might reasonably have been expected given the country's geographic remoteness from the European center of the movement and its modest standing among the powers. American initiative contributed to the formation of such multilateral agencies as the Universal Postal Union (1874) and, within the Western Hemisphere, the Pan American Union (1890). Although the determination of the dates of establishment of international organizations and of adherence by particular states is by no means an exact science, one can take it as approximately correct that by 1900 the United States was a member of ten international bodies, and that by the outbreak of World War I it participated in twenty-seven, as against twenty-eight for Great Britain and thirty-six for France.
This record would seem to substantiate Henry Reiff's assertion that "The United States … is a veteran, if not an inveterate, joiner of unions or leagues of nations," despite its failure to affiliate with the League of Nations and the Permanent Court of International Justice. America's record of interest and involvement in international organization made it less surprising that President Woodrow Wilson took the lead in creating the League of Nations than that the United States refrained from joining it. The American rejection of the league, historically considered, was an aberration rather than a continuation of settled policy regarding international organization. Moreover, it did not presage a drastically altered policy. Although the United States never accepted membership, it gradually developed cooperative relationships with the league in many areas of activity and ultimately assumed a formal role in several of its component parts. In the final analysis the United States became a more active and more useful participant in the operation of the league than many of the states that were officially listed as members. In addition, between the world wars the United States continued to join organizations outside the league family to such an extent that by 1940 it held a greater number of organizational memberships than did Britain and France, the leading powers in the league. Following World War II the United States became the world's unchallenged leader in promoting and supporting the development of international organizations of every sort.