International attention to Shanghai grew in the 19th century due to its economic and trade potential at the Yangtze River. During the First Opium War (1839-1842); British forces temporarily held the city. The war ended with the 1842 Treaty of Nanjing; opening Shanghai and other ports to international trade.

In 1863; the British settlement; located to the south of Suzhou creek (Huangpu district); and the American settlement; to the north of Suzhou creek (Hongkou district); joined in order to form the International Settlement. The French opted out of the Shanghai Municipal Council; and maintained its own French Concession.

Citizens of many countries and all continents came to Shanghai to live and work during the ensuing decades; those who stayed for long periods called themselves 'Shanghailanders'. In the 1920s and 30s; some 20;000 so-called White Russians and Russian Jews fled the newly established Soviet Union and took up residence in Shanghai. By 1932; Shanghai had become the world's fifth largest city and home to 70;000 foreigners.