In the 9th century, josaku were also started to be founded in the present-day Iwate region, as Isawa-jo Castle was founded by SAKANOUE no Tamuramaro in 802, to which Chinju-fu (Pacification and Defense Headquarters) were relocated from Taga-jo Castle.
9世紀にはいると現在の岩手県地域にも城柵が作られはじめ、延暦21年（802年）に坂上田村麻呂により胆沢城が設置され、鎮守府が多賀城から移された。