March 29, 1896 - Isa District was formed when Kitaisa and Hishikari Districts were merged. The villages of Ōkuchi, Yamano, Hatsuki, Hishikari, Nishitara and Higashitara were formed.
April 1, 1918 - The village of Ōkuchi was elevated to town status to become the town of Ōkuchi. (1 town, 5 villages)
February 11, 1925 - The village of Higashitara was renamed to the village of Honjō.
April 29, 1940 - The village of Hishikari was elevated to town status to become the town of Hishikari. (2 towns, 4 villages)
November 10, 1940 - The village of Yamano was elevated to town status to become the town of Yamano. (3 towns, 3 villages)
April 1, 1954 - The towns of Ōkuchi and Yamano, and the villages of Nishitara and Hatsuki were merged to create the city of Ōkuchi. (1 town, 1 village)
July 15, 1954 - The town of Hishikari, and the village of Honjō were merged to create the town of Hishikari. (1 town)
November 1, 2008 - The town of Hishikari, along with the city of Ōkuchi, was merged to create the city of Isa.[1] Isa District was dissolved as a result of this merger.
