Administratively, Leningrad Oblast is divided into seventeen districts and a town of oblast significance, Sosnovy Bor. Lomonosovsky District is the only one in Russia which has its administrative center (the town of Lomonosov) located in the area of a different subject of Russian Federation (the federal city of Saint Petersburg, which is not a part of Leningrad Oblast). In terms of the area, the biggest administrative district is Podporozhsky District (); the smallest one is Lomonosovsky District (). Administrative and municipal divisions Differences with municipal divisions The municipal divisions of Leningrad Oblast are identical with its administrative divisions. All of the administrative districts of Leningrad Oblast are municipally incorporated as municipal districts, and the city of oblast significance is municipally incorporated as an urban okrug. History Until 1927 , 1708 Tsar Peter the Great issued an edict which established seven governorates. The description of the borders of the governorates was not given; instead, their area was defined as a set of towns and the lands adjacent to those towns. The present area of Leningrad oblast was a part of Ingermanland Governorate, which was renamed Saint Petersburg Governorate in 1710. The governorates were subdivided into uyezds, and uyezds into volosts. Eventually, parts of Saint Petersburg Governorate were split off to form separate governorates, such as Novgorod, Pskov, or Olonets Governorates. Vyborg Governorate, which was split off early, in 1812 was included into the Grand Duchy of Finland as the Viipuri Province, and in 1918 became a part of independent Finland. In 1913, Saint Petersburg Governorate was renamed Petrograd, and in 1924 Leningrad Governorate. The east and south of the current area of the oblast was transferred in 1727 to Moscow and Novgorod Governorates. After a sequence of administrative reforms, the northeastern part of the oblast ended up in 1801 in Olonets Governorate. In June 1918, five uyezds of Novgorod Governorate, including Tikhvinsky Uyezd, were split off to form Cherepovets Governorate, with the administrative center in Cherepovets. In 1922, Olonets Governorate was abolished, and Lodeynopolsky Uyezd (which contained all areas later transferred to Leningrad Oblast) was transferred to Petrograd Governorate. Thus, by 1927 the current area of the oblast was split between three governorates — Leningrad, Novgorod, and Cherepovets. Additionally, the areas adjacent to the Narva River, including the town of Ivangorod, were assigned to Estonia in 1920, following the Estonian War of Independence and the Treaty of Tartu, signed on February