Middleport began as a colony of the Dukedom of Gaien until it was occupied by the Kooluk Empire. Kooluk would agree to withdraw from the island under the condition that Middleport would become independent, breaking off all ties with Gaien. This was apparently done to help facilitate the gathering of Rune Cannon materials, which had recently been invented in the city. Following Kooluk's withdrawal, Middleport would be governed by Lord Schtolteheim Reinbach II.
Middleport's political neutrality helped it to become a thriving trade city and both overt regular trade and Reinbach II's underground trading in Rune Cannon materials, would cause the city to become very wealthy. The city would also become known as the birthplace of Rune Cannon technology.
The island would remain neutral throughout the Island Liberation War, although it agreed to let the Headquarters Ship visit and use the island for trade, recruitment and any other matters. Once the war ended, Middleport would become a founding member of the Island Nations Federation, with Reinbach III succeeding his father as Lord.
- Gensosuikoden Kiwami Encyclopedia, pages 481, 553