By the middle of the twentieth century, the textile industry was establishing itself more profitably in the American South, and some Maine cities began to de-industrialize as wages rose above those of the South. In 1937, the Lewiston-Auburn Shoe Strike involved 4,000 to 5,000 textile workers on strike in Lewiston and Auburn. It was one of the largest labor disputes state history. Shipbuilding also ceased in all but a few places, notably Bath and its successful Bath Iron Works, which became a notable producer of naval vessels during the Second World War and after. In recent years, however, even Maine's most traditional industries have been threatened; forest conservation efforts have diminished logging and restrictions on fisheries have likewise exerted considerable pressure along the coast. The last "heavy industry" in Maine, pulp and paper began to withdraw in the late 20th century, leaving the future of the Maine Woods an open question.