Never before and never after did Cologne grow as rapidly as in the 33 years between the demolition of the city wall in 1881 and the beginning of World War I in 1914. During this time, the population increased fivefold, and the area of the city expanded fiftyfold. Cologne grew so quickly that all standards shifted, even in the everyday lives of the people: underground sewage pipes were laid, gas lamps illuminated the night, horses disappeared from the streets to make way for trams, and cinemas and sports clubs became popular. The rapid urbanization brought hundreds of thousands of immigrants to the city. Farming villages transformed into industrial areas, entirely new neighborhoods emerged; the fluctuation of people was immense. This raised the question of who could truly be considered a Cologne resident and what "Cologne" actually meant. One of the theses of the book: Managing this massive change was essential.