Cimei Township is located at the southernmost tip of the Penghu Archipelago. It was named “Nanyu” or “Nandayu” at the initial stage of the Ching Dynasty. Since Cimeiyu is the largest island on the south of the Penghu Archipelago, people at the end of the Ching Dynasty and the initial stage of the Republic of China called it “Dayu”. During the Japanese Occupied Period, “Dayu” was a “She” under the jurisdiction of the “Wangan Zhuang”. It was then moved out of the “Wangan Zhuang” and became the “Dayu Zhuang” in August 1943, and changed to “Dayu Township” again on December 21, 1945. Later in 1949, Yen-Fu Liu, the County Mayor (the 4th mayor of Penghu County), invited local gentry to discuss the change of the place name in order to recall the staunch moral integrity and touching stories of the Cimei people. A report was submitted to the provincial government and the name of the township was changed from “Dayu Township” to “Cimei Township” upon approval of the provincial government. Now, Cimei Township has jurisdiction over Donghu, Xihu, Zhonghe, PInghe, Haifeng, and Nangang villages.
The Cimei Island is located at Longitude 119 degrees 40 minutes and latitude 23 degrees 16 minutes. It is about 29 nautical miles (36 kilometers) away from Magong, about 48 nautical miles away from Tainan on the east, and about 58 nautical miles away from Kaohsiung on the south. The area of the island is about 6.99 square kilometers with a circumference of 14.40 kilometers. It is a cut quadrangular islet and ranked fifth among the islands of the Penghu Archipelago.