The Knox–Porter Resolution was a joint resolution passed by the United States Congress to formally end the state of war with Germany post-World War I. Signed by President Warren G. Harding, the resolution officially terminated the war that had been declared in April 1917. The Senate ratified this resolution on March 19, 1921, followed by the House of Representatives on June 30, 1921. Harding's signing was a key moment, representing not just the end of military conflict but also a re-establishment of peace and normal diplomatic relations between the U.S. and Germany. It is noteworthy that this resolution was signed without a treaty, which was significant given the context of the Treaty of Versailles and the growing desire among Americans for a step away from European entanglements.

The resolution's signing had broader implications in American society as well. Harding advocated for a return to normalcy following the war, which resonated with a populace weary from military engagement and the dislocation caused by the war. It also marked the initiation of a new foreign policy approach for the U.S., focusing more on internal development and less on international commitments, which would characterize much of the interwar period. This articulation of American foreign policy increasingly steered the nation away from the League of Nations, of which many Americans were skeptical.

The resolution also encountered challenges and was subject to criticism, particularly from those who supported the League of Nations and a more engaged American role in international affairs. Nonetheless, it set the stage for a redefined geopolitical landscape in the years following the war and influenced the future of U.S.-European relations as the country grappled with its identity in a rapidly changing world.