Chiba Prefecture was settled in prehistoric times, as evidenced by the Jōmon period remains in every part of the region. The prefecture holds the largest kaizuka sea shell mounds in Japan, evidence of a large population in the prefecture that relied on the rich marine products of the Pacific Ocean and Tokyo Bay. Kofun burial mounds are found across the prefecture, with the largest group being in Futtsu along Tokyo Bay.
Asuka and Nara periods
In the Asuka period (538 – 710), under the Taika Reform of 654, the administrative structure of present-day Chiba Prefecture changed significantly. The historical province of Fusa Province, which may have covered much of Chiba and Ibaraki prefectures, was divided into two provinces: Shimōsa Province (also called Shimofusa) in the north and Kazusa Province in the southern area. Awa Province at the south of Chiba Prefecture, was separated from Kazusa Prefecture in 718. These administrative units existed until they were abolished and merged into Chiba Prefecture after the Meiji restoration. The central government established a kokubunji provincial temple in each province.
The imperial court gradually extended its authority over the three provinces in the Nara (710 – 794) and Heian (794 – 1185) periods. Shōen feudal estates were established across the three provinces, and the region became an important source of tax revenue, agricultural and other products to the capital in Kyoto. As the Heian period progressed, however, the kokushi provincial governors came to exert military power independent of the central government in Kyoto. The Chiba clan broke entirely with the imperial court and was instrumental in the establishment of the Kamakura shogunate.
Chiba Prefecture was established on June 15, 1873 with the merger of Kisarazu Prefecture and Inba Prefecture. The 1923 Great Kantō earthquake caused widespread destruction in Chiba Prefecture, notably in the southernmost part of the Bōsō Peninsula, where 1,300 residents were killed. Areas of the prefecture adjacent to Tokyo saw much damage, and mob violence against Koreans and other ethnic minorities occurred in the chaos after the earthquake in Funabashi, Ichikawa, and other areas. Koreans in several neighborhoods of Yachiyo were killed, and a tower was erected in 1972 near Yachiyodai Station to memorialize those killed in the incident. The militarization of Chiba Prefecture dates to the Russo-Japanese War (1904–1905). Coastal fortifications were built along Tokyo Bay as far south as Tateyama to protect the capital of the Japanese Empire from attack. In the 1930s the north and central areas of the prefecture became a center of large-scale military production, and military bases and fortifications were constructed in most coastal areas of the prefecture. After the United States took control of Saipan the northern part of the prefecture, most notably the city of Chiba and Chōshi, were firebombed. Much of the industrialized north of the prefecture was destroyed. Operation Coronet, one of two parts of Operation Downfall, was the planned land invasion of Tokyo in March 1946 by the United States. Coronet planned Kujūkuri Beach as one of two initial landing bases, the other being Hiratsuka via Sagami Bay. The U.S. First Army would enter at Kujūkuri, sweep across the Bōsō Peninsula, and meet the U.S. Eighth Army at Tokyo. After the atomic bombings of Hiroshima and Nagasaki but due to the surrender of Japan in 1945, the plan was never carried out.
During the Occupation of Japan (1945–1952) Chiba Prefecture was controlled by American forces from the second floor of the prefectural capitol building in the city of Chiba. Numerous other cities in the prefecture, including Chōshi to the north and Tateyama to the south, were used as bases of the occupation. The rich agriculture areas across the prefecture protected the region somewhat from the level of food shortage and starvation immediately following the war. The immediate post-war period was characterized by carefully planned industrial expansion in the north of the prefecture and the significant increase of agricultural production after land reforms across the prefecture. The Keiyō Industrial Zone brought together smaller industrial areas along the entirety of the western coast of Chiba Prefecture, and the industrial zone became, and remains an important center of heavy industrial production and large-scale port facilities in Japan. Cities to the northeast of the prefecture in close proximity to Tokyo were connected by rail to the capitol, and became and remain bedroom communities to Tokyo. Narita International Airport began operation in 1978 in Narita after much protest to replace the overcrowded Tokyo International Airport (Haneda Airport). The majority of international air traffic enters Japan via Chiba Prefecture. Agriculture, specifically of rice, and also vegetables to serve the Greater Tokyo Metropolitan Area expanded greatly and became a source of income to the northeast and central areas of the prefecture. Agriculture expansion of the central and southern regions of the prefecture was in contrast to the depopulation of these areas as a significant part of the population moved to the northeast of the prefecture as a result of the urbanization of Japan, a process that continues into the 21st century.
2011 Tōhoku earthquake and tsunami
The 2011 Tōhoku earthquake and tsunami affected areas as far south as Chiba Prefecture. While the loss of life and damage to housing and industry was far less than in the Tōhoku region, 20 people were killed in Chiba Prefecture, mostly from the tsunami that hit Asahi to the northeast of the prefecture and caused 13 deaths. An oil refinery fire, widely seen in the news media following the Tōhoku earthquake, was at the Cosmo Oil Chiba Refinery in Ichihara. Large liquefied petroleum gas (LPG) tanks burned from March 11–21, 2011. Soil liquefaction in areas of reclaimed land across the northern and western areas of Chiba Prefecture caused damage, primarily to housing. Chiba City, Funabashi, Narashino, and especially Urayasu were greatly affected. Radiation fallout from the Fukushima Daiichi nuclear disaster continues to affect densely populated cities to the northwest of the prefecture. As a result of permanent damage to housing stock due to soil liquefaction and evidence of radioactive materials, the population of Chiba Prefecture fell for the first time since 1920.