Polish People's Republic
The Polish People's Republic (, ) was a state in Central Europe that existed from 1947 to 1989, and the predecessor of the modern democratic Republic of Poland. With a population of approximately 37.9 million inhabitants near the end of its existence, it was the most populous state of the Eastern Bloc after the Soviet Union. Having a unitary Marxist–Leninist communist government, it was also one of the main signatories of the Warsaw Pact. The official capital since 1947 and largest city was Warsaw, followed by industrial Łódź and cultural Kraków.
Congress Poland
The "Kingdom of Poland" was created out of the Duchy of Warsaw, a French client state, at the Congress of Vienna in 1815 when the great powers reorganized Europe following the Napoleonic wars. The Kingdom was created on part of the Polish territory that had been partitioned by Russia, Austria and Prussia replacing, after Napoleon's defeat, the Duchy of Warsaw, set up by Napoleon in 1807. After Napoleon's 1812 defeat, the fate of the Duchy of Warsaw was 
dependent on Russia. Prussia insisted on the Duchy being completely eliminated, but after Russian troops reached Paris in 1812, Tsar Alexander I originally intended to annex to the Duchy the Lithuanian-Belarusian lands, now controlled by the Tsardom, which used to be a part of the First Polish Republic and to unite thus created Polish country with Russia. Both Austria and England did not approve of that idea, Austria issuing a memorandum on returning to the 1795 resolutions, this idea supported by England under George IV and Prime Minister Robert Jenkinson and the English delegate to the Congress, Robert Stewart, Viscount Castlereagh, so in effect the Tsar, after the so-called Hundred Days, established the Kingdom of Poland and the 1815 Congress of Vienna approved. After the Congress, Russia gained a larger share of Poland (with Warsaw) and, after crushing an insurrection in 1831, the Congress Kingdom's autonomy was abolished and Poles faced confiscation of property, deportation, forced military service, and the closure of their own universities. The Congress was important enough in the creation of the state to cause the new country to be named for it. The Kingdom lost its status as a sovereign state in 1831 and the administrative divisions were reorganized. It was sufficiently distinct that its name remained in official Russian use, although in the later years of Russian rule it was replaced with the "Privislinsky Krai" (Russian: Привислинский Край). Following the defeat of the November Uprising its separate institutions and administrative arrangements were abolished as part of increased Russification to be more closely integrated with the Russian Empire. However, even after this formalized annexation, the territory retained some degree of distinctiveness and continued to be referred to informally as Congress Poland until the Russian rule there ended as a result of the advance by the armies of the Central Powers in 1915 during World War I.