Why are Shanghai all surnamed Yu?

Because of historical reasons and geographical location. Shanghai was an important commercial port city in Qing Dynasty, which attracted a large number of businessmen and immigrants to settle down. At that time, the Yu family was mainly distributed in Zhejiang and Jiangsu, which were adjacent to Shanghai and had convenient transportation, so many Yu families also came to Shanghai with the flow of business and population. The Yu family originated in China and is an ancient surname. According to historical records, the surname Yu first appeared in the Spring and Autumn Period, when Yu was a small country located in today's Shandong Province.