Consequently, the population climbed rapidly. Towns with only 2000 to 5000 people in the early 19th century grew in the following 100 years to over 100,000. Skilled mineworkers were recruited from other regions to the Ruhr's mines and steel mills and unskilled people started to move in. From 1860 onwards there was large-scale migration from Silesia, Pomerania, East Prussia and Posen to the Ruhr. Many of them were Polish speakers and they were treated as second class citizens. In 1899 this led to a revolt in Herne of young Polish workers, who later established a Workers' Union. Skilled workers in the mines were often housed in "miners' colonies", built by the mining firms. By the end of the Prussian Kingdom in 1870, over 3 million people lived in the Ruhrgebiet and the new coal-mining district had become the largest industrial region of Europe.