The is a river in Chiba Prefecture, Japan. It is 37.3 kilometres (23.2 mi) in length and has a drainage area of 222 square kilometres (85.7 sq mi). Under the Rivers Act of 1906 the Ichinomiya is designated as a Class 2 River. The river basin of the Ichinomiya was a social, cultural, and economic center of Kazusa Province

Kazusa Province

was a province of Japan in the area of modern Chiba Prefecture. It lies on in the middle of the Bōsō Peninsula , whose name takes its first kanji from the name of Awa Province and its second from Kazusa and Shimōsa Provinces. Its abbreviated form name was or .Kazusa is classified as one of the...

 in pre-modern Japan. Although very shallow, the river was used to transport sardines from Kujukuri Beach

Kujukuri Beach

is a sandy beach located on the east coast of the Bōsō Peninsula in Chiba Prefecture, Japan. Lying within 60 km of Tokyo and being the second longest beach in Japan, it is a popular swimming and surfing destination for inhabitants of Greater Tokyo....

 to Tokyo Bay

Tokyo Bay

is a bay in the southern Kantō region of Japan. Its old name was .-Geography:Tokyo Bay is surrounded by the Bōsō Peninsula to the east and the Miura Peninsula to the west. In a narrow sense, Tokyo Bay is the area north of the straight line formed by the on the Miura Peninsula on one end and on...

 via until the beginning of the Meiji period

Meiji period

The , also known as the Meiji era, is a Japanese era which extended from September 1868 through July 1912. This period represents the first half of the Empire of Japan.- Meiji Restoration and the emperor :...

.

Geography

The source of the Ichinomiya River is in the Fukusawa District of Chōnan

Chonan, Chiba

is a town located in Chōsei District, Chiba, Japan.As of 2010 estimates, the town had a population of 9,154 and a density of 140 persons per km². The total area was .- Geography :...

, and crosses the southern part of the Kujukuri Plain through Ōtaki

Otaki, Chiba

is a town located in Isumi District, Chiba, Japan, occupying the center of the Bōsō Peninsula. The town is known for its association with Edo period general Honda Tadakatsu and its prominent castle. As of 2010, the town had an estimated population of 10,794 and a population density of 83.1 persons...

, Nagara

Nagara, Chiba

is a town located in Chōsei District, Chiba, Japan. As of Mar. 1, 2010, the town had an estimated population of 8,117 and a density of 172 persons per km². The total area is 47.20 km².- Geography :...

, Mobara

Mobara, Chiba

is a city located in Chiba Prefecture, Japan. As of September 2010, the city has an estimated population of 92,449 and a population density of 924 persons per km². The total area is 100.01 km².-Geography:...

, and Mutsuzawa

Mutsuzawa, Chiba

is a town located in Chōsei District, Chiba, Japan.As of 2010, the town has an estimated population of 7,419 and a density of 208 persons per km². The total area is 35.59 km².-Geography:...

, and the town of Ichinomiya

Ichinomiya, Chiba

is a town located in Chōsei District, Chiba, Japan. As of 2010, the town had an estimated population of 12,079and a density of 525 persons per km². The total area was 23.02 km².-Geography:...

. It pours into the Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 in the Ichimatsu District of the village of Chōsei

Chosei, Chiba

is a village located in Chōsei District, Chiba, Japan. As of 2010, the village had an estimated population of 14,547 and a density of 514 persons per km². The total area was 28.32 km².-Geography:...

.

Tributaries

• Mizusawa River
• Habu River
• Chōrakuji River
• Obuta River
• Satsubo River
• Tsurue River
• Aku River
• Toyoda River
• Sanzu River
• Mizugami River