Past Mergers
There have been three waves of merger activity between Japanese municipalities, the largest being in 2005. This recent peak is sometimes referred to as "the great Heisei mergers" (平成の大合併, heisei-no-daigappei?) as a way of distinguishing it from the earlier two.
The first peak of mergers, known as "the great Meiji mergers" (明治の大合併, meiji-no-daigappei?), happened in 1889, when the modern municipal system was established. Before the mergers, existing municipalities were the direct successors of spontaneous hamlets called hanseison (藩政村?), or villages under the han system. The rump han system is still reflected in the postal system for rural areas as postal units called ōaza (大字?). The Meiji mergers slashed total municipalities from 71,314 to 15,859.
The second peak, called "the great Shōwa mergers" (昭和の大合併, shōwa-no-daigappei?), took place in the mid-1950s. It reduced the number of municipalities by over half, from 9,868 to 3,472.
Municipal mergers in the island prefectures of Hokkaidō and Okinawa, have followed different tracks.
Read more about this topic: Municipal Mergers And Dissolutions In Japan