Shanghai is one of the four municipalities of the People's Republic of China. It is located on the southern estuary of the Yangtze, with the Huangpu River flowing through it. With a population of 24.28 million as of 2019, it is the most populous urban area in China and the second most populous city proper in the world. Shanghai is a global center for finance, innovation and transportation and the Port of Shanghai is the world's busiest container port.
Originally a fishing village and market town, Shanghai grew in importance in the 19th century due to trade and its favorable port location. The city was one of five treaty ports forced open to foreign trade after the First Opium War. The Shanghai International Settlement and the French Concession were subsequently established. The city then flourished, becoming a primary commercial and financial hub of the Asia-Pacific region in the 1930s. During the Second Sino-Japanese War, the city was the site of the major Battle of Shanghai. After the war, with the CPC takeover of mainland China in 1949, trade was limited to other socialist countries and the city's global influence declined.