Duchy of Lithuania Duchy of Lithuania Duchy of Lithuania (; ) was a state-territorial formation of ethnic Lithuanians, that existed from the 13th century until 1413. Most of the time it was a constituent part and a nucleus of the Grand Duchy of Lithuania. Other alternative names of the territorial formation, used in different periods, were Aukštaitija or Land of Lithuania (13th century), Duchy of Vilnius (14th – early 15th centuries), Lithuania Propria or simply Lithuania (in a narrow sense). The formation emerged in the central and eastern part of the present-day Lithuania, known as Aukštaitija, as the Lietuva Land (). It is
Act of Independence of Lithuania the first Cabinet of Lithuania was formed, and the Council of Lithuania gained control over the territory of Lithuania. Independent Lithuania, although it would soon be battling the Wars of Independence, became a reality. The laconic Act is the legal basis for the existence of modern Lithuania, both during the interwar period and since 1990. The Act formulated the basic constitutional principles that were and still are followed by all Constitutions of Lithuania. The Act itself was a key element in the foundation of Lithuania's re-establishment of independence in 1990. Lithuania, breaking away from the Soviet Union, stressed that it