This area of Ohio became a center of resource development and industrialization through the mid-20th century. It was a center of the steel industry, receiving iron ore shipped through the Great Lakes from Minnesota, processing it into steel products, and shipping these products to the east. This industry stimulated the development of great freight lakers, as the steam ships were known, including the first steel ships in the 20th century. Railroads took over some of the freight and commodity transportation from the lake ships. In the late 19th and early 20th centuries, these cities attracted hundreds of thousands of European immigrants and migrants (both black and white) from the rural South to its industrial jobs.