Mikhail Kalinin in the context of "Kremlin Wall Necropolis"

The Declaration and Treaty on the Formation of the Union of Soviet Socialist Republics (Russian: Декларация и договор об образовании Союза Советских Социалистических Республик) officially created the Union of Soviet Socialist Republics (USSR), commonly known as the Soviet Union. It de jure legalised a political union of several Soviet republics that had existed since 1919 and created a new federal government whose key functions were centralised in Moscow. Its legislative branch consisted of the Congress of Soviets of the Soviet Union and the Central Executive Committee of the Soviet Union (TsIK), while the Council of People's Commissars composed the executive.

The Treaty, along with the Declaration of the Creation of the USSR was approved on 30 December 1922 by a conference of delegations from the Russian SFSR, the Transcaucasian SFSR, the Ukrainian SSR and the Byelorussian SSR. The Treaty and the Declaration were confirmed by the First All-Union Congress of Soviets and signed by heads of delegations – Mikhail Kalinin, Mikhail Tskhakaya, and Grigory Petrovsky, Alexander Chervyakov respectively on December 30, 1922. The treaty provided flexibility to admit new members. Therefore, by 1940 the Soviet Union grew from the founding four (or six, depending on whether 1922 or 1940 definitions are applied) republics to 16 republics.

The First All-Union Congress of Soviets (Russian: I Всесоюзный съезд Советов, romanized: 1 Vsesoyuznyy s"ezd Sovetov) was a congress of representatives of Soviets of workers, peasants and Red Army deputies, held on December 30, 1922 in Moscow. The congress was attended by 2215 delegates (1727 from the Russian Socialist Federative Soviet Republic, 364 from the Ukrainian Socialist Soviet Republic, 91 from the Transcaucasian Socialist Federative Soviet Republic, 33 from the Belarusian Socialist Soviet Republic). Kalinin was elected chairman of the congress, but Vladimir Lenin, who was not present at the congress due to illness, was elected honorary chairman of the congress. More than 90% of the delegates were members of the Russian Communist Party, 2 left-wing social federalists of the Caucasus, 1 anarchist and 1 member of the Jewish Social Democratic Party.

The congress approved the Declaration and the Treaty on the Formation of a New State – the Union of Soviet Socialist Republics. 4 states have united in the Soviet Union: Russian Socialist Federative Soviet Republic, Ukrainian Socialist Soviet Republic, Belarusian Socialist Soviet Republic, Transcaucasian Socialist Federative Soviet Republic. In addition, the congress elected the Central Executive Committee of the Soviet Union.