Treaty on the Creation of the USSR
The first congress was held on 30 December 1922 in Moscow with delegates from Russian Soviet Federative Socialist Republic, the Ukrainian Soviet Socialist Republic, the Transcaucasian Socialist Federative Soviet Republic and the Belarusian Soviet Socialist Republic. The Congress approved the Treaty on the Creation of the USSR, the basis of the 1924 Soviet Constitution, and thus formally created the Soviet Union with the four as founding Union Republics.