city, Gumma ken (prefecture), Honshu, Japan, on the Ryomo Line (railway) between Takasaki and Ōyama. Isesaki prospered as a market town around a castle built in the early Tokugawa period (1603–1867) and was known for its silk manufacture, which employed a large number of women. After the Meiji Restoration (1868) the city rapidly became a centre of the silk-weaving industry; synthetic textiles were introduced in 1957. Other industrial products include machinery, transport equipment, and electrical appliances. Pop. (2005) 202,447.