Most of the city of Ishinomaki was formerly within the district. From 2006, the district has consisted only of the town of Onagawa. As of 2021, the district has an estimated population of 5,636 and a population density of 86.2 persons per km2. The total area was 65.35 km2.
During the Edo period under the Tokugawa shogunate, the district was within Mutsu Province and was under the control of the Date clan of Sendai Domain. In 1869, following the Meiji restoration, Mutsu Province was divided, with the area of Oshika District becoming part of Rikuzen Province, and from 1872, part of Miyagi Prefecture.
In 1889, with the establishment of the municipalities, Oshika District was administratively divided into 2 towns (Ishinomaki and Watanoha) and 6 villages.