is a city located in Saitama Prefecture, Japan. The city was founded on April 1, 1933.As of March 1, 2012, the city has an estimated population of 579,069, the second largest in Saitama Prefecture after Saitama City, and a population density of 9,344 persons per km². The total area is 61.97 km². It is the Greater Tokyo Area's 9th most populated city (after Hachioji).On October 11, 2011, Kawaguchi City absorbed the neighboring city of Hatogaya.HistoryAfter the last ice age, during early and middle Jomon period, most of the area which is now Kawaguchi City were under sea level except for the area which is now Omiya Tableland. (Japanese: ) Ancient people living in this area left several shell heaps, in which a lot of shells, Jomon pottery, and pit houses were dug up.In Kofun period, countless barrows were constructed particularly in the west of Japan. Some barrows were also found in Kawaguchi, the largest one is Takainari Barrow, which was destroyed because of the use of the soil in 1960.In middle ages, Kawaguchi was part of Musashi Province, which included entire Saitama, Tokyo, and part of Kanagawa Prefecture. It is not known when people started using the name Kawaguchi, but in a tale of war named Gikeiki, which was reportedly written in around 1300, there was a name of Ko Kawaguchi, that means little Kawaguchi. However, it is not proven that the name designated current Kawaguchi.