Why were Shanghainese assigned to other places before?

Because at that time, all the work was assigned by the state and the stalls were arranged collectively. You must buy goods by ticket.

Before 1949, the old immigrants mainly came from Jiangsu and Zhejiang provinces. Shanghai dialect at that time was three-quarters the same as Shanghai suburban dialect today. After 1949, the native place and composition of Shanghainese became more diverse. Since then, Shanghai dialect has been deeply influenced by Ningbo dialect and other dialects. Shanghai dialect is one quarter the same as Shanghai suburban dialect today, which basically determines the dialect characteristics of Shanghai downtown dialect today.

Shanghai, referred to as "Shanghai" for short, is China's international economic, financial, trade, shipping and scientific and technological innovation center approved by the State Council, and is the core city of provincial administrative regions, municipalities directly under the Central Government, national central cities, megacities and Shanghai metropolitan area.