[3] Per Japanese census data,[6] the population of Ichinohe peaked in the 1950s has declined steadily over the past 60 years.

The area of present-day Ichinohe was part of ancient Mutsu Province, and has been settled since at least the Jōmon period.

The neighboring villages of Anetai, Kozuya, Chōkai, and Namiuchi were merged with Ichinohe on January 1, 1955.

Ichinohe has a mayor-council form of government with a directly elected mayor and a unicameral town council of 14 members.

In terms of national politics, the town is part of Iwate 2nd district of the lower house of the Diet of Japan.