occupied Estonia in 1941–1944, considered it as an important source of fuel. However, they failed to begin full-scale extraction. After the war, the next occupier of Estonia, the Soviet Union, required constantly increasing quantities of oil shale for its industries and extraction greatly expanded. Kohtla-Järve, as the main settlement in the mining area, received city status on 15 June 1946. Since that time, during the next twenty years, there was a process of administrative amalgamation of neighboring settlements within the limits of Kohtla-Järve. Kohtla and Kukruse were added to the city in 1949; Jõhvi, Ahtme and Sompa in 1960. The town of Kiviõli and the boroughs of Oru, Püssi and Viivikonna were subordinated to the city in 1964. Thus, Kohtla-Järve greatly expanded, becoming a city with a unique layout, as its parts remained scattered among woods, agricultural areas and oil shale mines. Total population of the city increased mainly by workers sent from different parts of Soviet Union, reaching (with subordinated settlements) 90,000 in 1980. After the end of the Soviet Union occupation, Estonia regained independence in August 1991, and thereafter the number of city districts decreased, as Jõhvi, Kiviõli and Püssi became officially separate towns. The volume of oil shale extraction and processing decreased dramatically during the 1990s, and many Kohtla-Järve citizens moved to Tallinn or Russia, due to high unemployment in Ida-Viru County. Religion Economy Kohtla-Järve is known for its chemical industry. It is the headquarters of Viru Keemia Grupp, an Estonian holding group of oil shale industry, power generation, and public utility companies. Eastman Chemical Company also has a manufacturing site located in Kohtla-Järve. Since 2006, the Ukrainian DF Group has owned a fertilizer plant in Kohtla-Järve – it has (through its Austria and Cyprus based intermediaries) 100% ownership of AS Nitrofert. Established in 1993, AS Nitrofert was (as of 2006) the only plant to produce fertilizers in Estonia and during the peak of its production used 25% of the total volume of natural gas in Estonia. Geography Kohtla-Järve has a unique layout. The districts of the city are scattered across the northern part of Ida-Viru County in a considerably large area. The distance between Järve and Oru districts is about 20 km. Districts The city is subdivided into five administrative districts (): The populations of many of the smaller exclaves have rapidly declined since the 1990s. Before the Estonian administrative reform of 2017, Viivikonna and Sirgala