Koga

City, Ibaraki ken (prefecture), eastern Honshu, Japan. It lies at the confluence of the Omoi and Watarase rivers. An important river port, Koga was a castle town and post town on the Nikko-kaido (Nikko Highway) in the Tokugawa period (1603 - 1867). It became a major trade centre for the surrounding agricultural region after the Tohoku Main Line railway opened in 1891. Silk manufacture, introduced