city, Oita ken (prefecture), northern Kyushu, Japan. It lies along the mouth of the Yamakuni River facing the Inland Sea. The city developed around a castle built in 1587 by the Kuroda daimyo family. Industrial development began with the introduction of textile manufacturing in 1896. Nakatsu is now a commercial centre for the porcelain, steel, rice, and silk produced in the surrounding region. The city park, on the old castle site, contains a memorial to Nakatsu's native son Fukuzawa Yukichi (1835-1901), who founded Keio Gijuku (now Keio University) in Tokyo. Pop. (2005) 84,368.
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