Before industrialization the Keiyō region was originally home to
nori seaweed collection, the
shellfish industry, mixed small-scale fishing and agricultural villages, and
beach resorts. The
Keihin region, spanning west from Tokyo to
Yokohama, was developed after
World War I. With the rapid development of the
defense industry in Japan from the beginning of the
Shōwa period in 1926, a plan for the
decentralization of industry from the immediate Tokyo area was planned in 1935. The Keiyō Industrial Region was fully developed after
World War II. Some
land reclamation had been carried out in coastal areas of Tokyo Bay as part of the industrialization of Japan in the early 20th century. Reclaimed land areas replaced traditional fishing areas and supported small factories. The construction of the
Kawasaki Steel Works in Chiba City in 1953 marked the beginning of the large-scale construction of
heavy industry infrastructure in the industrial zone, and other industries soon followed. The
deepwater ports of the Keiyō Industrial Zone were built starting in the 1950s.
Thermal power generators were built, and large tracts of land were reclaimed from the bay for expansion of the Keiyō region. Keiyō was significantly expanded in the 1960s.
Heavy metal and
chemical production were among the highest in Japan by the 1970s. ==Industries==