The historical document that sanctioned the establishment of the United Nations in 1945 is the UN Charter. Adopted in the wake of World War II, the Charter aimed to promote international cooperation, ensure peace and security, and foster respect for human rights. It provided a framework for the UN's operations and defined the roles of its key organs, including the General Assembly and Security Council. The establishment of the UN marked a significant effort by nations to prevent future conflicts and work collaboratively toward global governance and development.