One hundred years after President Woodrow Wilson led Americans into the Great War, this essay ponders various counterfactual scenarios based on the assumption that the United States had not become a belligerent power in 1917. The methodological introduction makes a case for counterfactual analysis as a useful and indeed indispensable tool of historians. The second part demonstrates that contemporaries, including Wilson himself, did not consider American entry into the war a foregone conclusion. The third section looks at the possible consequences of continued American neutrality on the international position of the United States, while the fourth part focuses on the question which major domestic developments would have been unlikely had America remained neutral. Had the United States stayed out of the Great War, America's international role in the postwar world would not been very different from what it actually was in the 1920s, but the nation would have been spared the spasms of war hysteria that altered domestic politics.