industrial region in east-central Japan that, along with the Keihin Industrial Zone, is part of the Tokyo-Yokohama metropolitan area. Keiyō is neither an administrative nor a political entity. It occupies part of Chiba prefecture (ken) on the Bōsō Peninsula, along the northeastern shore of Tokyo Bay, and lies just east of Tokyo. This area along the bay was formerly used for seaweed collection, fishing, and resorts. Development of heavier industry began with construction of a steel plant in Chiba city in 1952. Other iron and steel, chemical (including petrochemical), and shipbuilding industries then migrated to Keiyō owing to industrial decentralization in Keihin across the bay. Deepwater ports and thermal power generators were built, and large tracts of land were reclaimed from the bay for expansion of the Keiyō region. Further development in Keiyō took place during the 1960s. By the mid-1970s, production of heavy metals and chemicals in Keiyō was the highest among Japan's industrial regions. Cities in Keiyō include Chiba, Funabashi, Kisarazu, and Kimitsu. Rail and highway connections are extensive.