The original territory was east–west long from the Ōu Mountains to the Pacific Ocean, including current Sendai, Shiogama, and Tagajō cities.
The province capital of Mutsu was moved to Taga (modern Tagajō) from the Koriyam site of Natori District in 724.
Taga continued to be the capital in the Kamakura period, but the city center moved to west Iwakiri.
In 1190 Isawa Iekage was appointed as the Governor Acting in Absence of Mutsu Province, charged with restoring order after the Revolt of Ōkawa Kanetō.
In addition to the Rusu, some samurai clans were known in southern and western parts of the district, including Ōkōchi, tenacious warriors for the Southern Court; Kokubun, the lord around the provincial temple (Kukubun-ji) of Mutsu; Hachiman clan, descendants of a past vice-governor of Mutsu.
When Masamune surrendered to the new shogun Toyotomi Hideyoshi in 1590, Rusu was abandoned and Kokubun was formally regarded a subject of Date.