In the 1880s many people in upper- and middle-class society were unaware of the dangerous conditions in the slums among poor immigrants. After the Civil War, the country transformed into an industrial superpower and became largely urban. Also, a wave of unskilled southern European, eastern European, Asian, and Jewish immigrants came to settle in the "promised land" of the United States. This migration was vastly different from the previous booms due to the influx of non-western European and non-Protestant individuals, therefore making the split between the "new" and "old" immigrants much larger. In the 1880s, over 5.2 million immigrants came to the United States, with many of these people staying in New York City. This increased New York City's population 25%, therefore making the tenement problem much more extreme.