The historical figure known for playing a crucial role in the founding of the United Nations is Harry S. Truman. As President of the United States after World War II, Truman supported the establishment of the UN to promote peace and prevent future conflicts. His leadership during the Bretton Woods Conference helped lay the groundwork for international cooperation and economic stability. Truman's commitment to democracy, human rights, and multilateralism informed his vision for the UN, and he recognized its potential to foster global collaboration. His efforts significantly shaped the organization’s foundational principles.