In July 28, 1945, with World War II coming to a close, the U.S. Senate indicated the sea change in American attitudes toward U.S. involvement in world affairs by approving the charter for the United Nations.
The U.N. charter' mission would be to provide the “foundation and cornerstone on which the international organization to keep the peace will be built.”
At its founding, the UN had 51 member states; there are now 193.