Short answers, pulled from the story.
Franklin D. Roosevelt drafted the final text of the declaration on the 29th of December 1941 inside the White House. He worked alongside British Prime Minister Winston Churchill and his own aide Harry Hopkins.
The Big Four signed the declaration officially on the 1st of January 1942 at the Arcadia Conference in Washington D.C. Representatives from twenty-two other governments added their signatures the following day on the 2nd of January 1942.
These four nations were the United States, the United Kingdom, the Soviet Union, and China. The initial group also included four dominions of the British Commonwealth: Australia, Canada, New Zealand, and South Africa.
The document incorporated suggestions from the Soviet delegation but excluded France due to its occupation by Germany. France eventually joined the ranks of the signatories after its liberation.
The Declaration by United Nations served as the direct basis for the modern United Nations organization. The UN Charter formalized this legacy when fifty countries signed it on the 26th of June 1945.