Kohtla-Järve is a city and municipality in northeastern Estonia, founded in 1924 and incorporated as a town in 1946. The city is highly industrial, and is both a processor of oil shales and is a large producer of various petrochemical products. During the 1944–1991 Soviet occupation, large numbers of immigrant workers from Russia and other parts of the former USSR were brought in to populate the rapidly growing city. The population in the Kohtla-Järve area which had been, as of 1934 census, over 90% ethnic Estonian, became overwhelmingly non-Estonian in the second half of the 20th century. According to more recent data (as of 2006) 21% of the city's population are ethnic Estonians; most of the rest are Russians. Kohtla-Järve is the fifth-largest city in Estonia in terms of population. Kohtla-Järve is unusual among the municipalities of Estonia due to its territory being made of several discontiguous parts. The two main parts, Järve (Kohtla-Järve proper) and Ahtme, both with populations around 20,000, are located about 10 km apart. Several other settlements in north-eastern Ida-Viru county, connected to oil shale mining, are administered as districts of Kohtla-Järve. During most of the period of the Soviet occupation, the town of Jõhvi was also incorporated into Kohtla-Järve. History The history of Kohtla-Järve is closely tied to the history of extraction of oil shale – the main mineral of Estonia. There is evidence that a number of settlements existed on the territory of modern Kohtla-Järve since the High Middle Ages. In the Danish Land Book, Järve and Kukruse villages were first mentioned in 1241 by the names Jeruius and Kukarus respectively, and Sompa village in 1420 by the name Soenpe. Its German name was Kochtel-Türpsal. Local residents were aware of oil shale's flammable capability in ancient times, but its industrial extraction in Estonia began only in the 20th century. In 1916, researches showed that oil shale could be used both as fuel and as a raw material for chemical industry, and mining started near Järve village. In 1919, the Estonian State Oil Shale Industrial Corporation was formed and extraction by shaft and open-pit mining was extended. Settlements for workers began to appear adjacent to the mines. In 1924 the oil shale processing factory was built near Kohtla railway station, and the nearby settlement, named Kohtla-Järve, started to grow. During World War II the value of the Estonian oil shale deposit grew. The Germans, who