The Russian Soviet Federative Socialist Republic (Russian SFSR or RSFSR), previously known as the Russian Soviet Republic and the Russian Socialist Federative Soviet Republic, and unofficially as Soviet Russia, was an independent federal socialist state from 1917 to 1922, and afterwards the largest and most populous constituent republic of the Soviet Union (USSR) from 1922 to 1991, until becoming a sovereign part of the Soviet Union with priority of Russian laws over Union-level legislation in 1990 and 1991, the last two years of the existence of the USSR. The Russian SFSR was composed of sixteen smaller constituent units of autonomous republics, five autonomous oblasts, ten autonomous okrugs, six krais and forty oblasts. Russians formed the largest ethnic group. The capital of the Russian SFSR and the USSR as a whole was Moscow and the other major urban centers included Leningrad (Petrograd until 1924), Stalingrad (Volgograd after 1961), Novosibirsk, Sverdlovsk, Gorky and Kuybyshev. It was the first socialist state in history.