It became an industrial town, formerly the economic centre of Kosovo because of the nearby Trepča Mines. It grew in size as a centre of trade and industry with the completion of the railway line to Skopje in 1873–1878, which linked Mitrovica to the port of Thessaloniki. Another line later linked the town to Belgrade and Western Europe. During World War II, the city was part of Axis-occupied Serbia. In 1948, Mitrovica had a population of 13,901 and in the early 1990s of about 75,000.