Major European cities grew so rapidly during this period that housing could not keep up.

Apartments were divided and subdivided, creating quarters of ever-shrinking size.

In 1875, forty percent of all urban households in Germany squeezed into a single heatable room.

Another consequence of the influx of working people was to segregate cities by social class.

Certain areas became largely and distinctively working class, while others grew more exclusive and well to do.

Most interactions now took place within the vertical—and inherently unequal—grid of work.

As a result, people from different levels of the social hierarchy interacted with one another less as neighbors who experienced certain similar concerns and more as members of isolated castes who increasingly viewed each other with fear, suspicion, and even contempt.

The urban redevelopment that transformed Paris during this period only reinforced such social and cultural shifts.