Union of Soviet Socialist Republics

former country 1922–91 in eastern Europe and northern Asia bordering on the Arctic and Pacific oceans and Baltic and Black seas; capital Moscow area 8,649,512 square miles (22,402,236 square kilometers) ◆The U.S.S.R., a union of constituent republics (Armenia, Azerbaijan, Belorussia, Estonia, Georgia, Kazakhstan, Kyrgyzstan, Latvia, Lithuania, Moldavia, Russia, Tajikistan, Turkmenistan, Ukraine, and Uzbekistan), existed from 1922 to 1991 and during that time was the largest country in the world in terms of land area.