On March 22, 2005 - the old city of Nagato absorbed the towns of Heki, Misumi and Yuya (all from Ōtsu District) to create the new and expanded city of Nagato. Ōtsu District was dissolved as a result of this merger.
On March 20, 2006 - the old city of Iwakuni absorbed the towns of Kuga, Mikawa, Miwa, Nishiki, Shūtō and Yū, and the village of Hongō (all from Kuga District) to create the new and expanded city of Iwakuni. There are no longer any villages in Yamaguchi Prefecture with this merger.
On March 21, 2008 - the towns of Mitō and Shūhō (both from Mine District) were merged into the expanded city of Mine. Mine District was dissolved as a result of this merger. [1]
On January 16, 2010 - the town of Atō (from Abu District) was merged into the expanded city of Yamaguchi.