Chongming County is the only under the jurisdiction of Shanghai, China. The county consists of three main islands: Chongming Island ; Changxing Island; and Hengsha Island. These are low-lying alluvial islands in the mouth of the Yangtze River. With an area of 1041 km? Chongming Island is the second largest island in the People's Republic of China after Hainan. The island first emerged in 618 due to a change in the water level of the river.
Once the most rural area of Shanghai, it is now the subject of a major urban and agricultural master-plan led by Philip Enquist of . With the construction of a trans- tunnel, the island is expected to increase in population while incorporating specialized agriculture in a sustainable design. It is also a major relocation centre for migrants from Three Gorges Dam area. Chongming has an area of 1041.38 km? and a population of 694,600 as of 2001. The city of Dongtan is currently being planned in this county.
Chong Ming National Forest Park is also located there.