For most of the Seine department's existence, its prefect also exercised direct authority over the City of Paris as well.
With the growth of Paris and its suburbs over the next 150 years, the population of the Seine department increased tremendously.
By 1968 it contained 5,700,754 residents (45% of them living in the City of Paris, 55% in the suburbs), making it by far the most populous department of France.
The breakup of the Seine department involved the following changes: Taken together, Hauts-de-Seine, Val-de-Marne and Seine-Saint-Denis are known in France as the Petite Couronne (meaning "small ring"), as opposed to the Grande Couronne ("large ring") of the more distant suburbs.
This new population growth after a long period of decline is comparable to what is observed in the central areas of other large Western metropolises such as Inner London.