Named for the Si River, it existed intermittently from 580 to 1912, during which time the relative position of a zhou within Chinese administrations varied.
The same name Sizhou was used for the town used as the seat of the prefectural or subprefectural government, which also varied, and is preserved in modern Anhui's Si County and Sicheng.
The administrative region of Si Prefecture in the Tang dynasty is in the border area of modern northwestern Jiangsu and northern Anhui.
It probably includes parts of modern: Under the Qing, Si Subprefecture formed a division of Jiangnan Province.
The seat of government was subsequently moved first to Xuyi in what is now Jiangsu's Huai'an Prefecture and Si County in Anhui.