Why is there Pudong County in the 1958 Shanghai Municipal District Map?

The eastern suburbs and Dongchang District merged to form Pudong County. In 1958, Pudong was first included in the administrative map of China as an administrative division. The eastern suburbs and Dongchang District were merged to form Pudong County, so Pudong County is included in the map of Shanghai Municipal District. Shanghai, referred to as "Hu", also known as "Shen", is China's largest economic center and an important international financial center city. It is one of the first batch of coastal open cities.