Seine-et-Oise

Seine-et-Oise was a département of France encompassing the western, northern, and southern parts of the metropolitan area of Paris. Its préfecture (capital) was Versailles and its official number was 78. Seine-et-Oise was abolished in 1968 as part of the reorganization of the départements of the Paris metropolitan area.

Seine-et-Oise was created on 4 March 1790. Its name comes from the two main rivers (Seine River and Oise River) flowing through it.

At its dissolution in 1968, Seine-et-Oise consisted of 688 suburban and rural communes completely surrounding the Seine département although it was at its narrowest just east of Seine between that département and the Seine-et-Marne département which still exists today. It had an area of 5,658 km² (2,184 sq. miles). The division of Seine-et-Oise into arrondissements changed many times. At its disappearance it had ten arrondissements: Argenteuil, Étampes, Mantes, Montmorency, Palaiseau, Pontoise, Le Raincy, Rambouillet, Saint-Germain-en-Laye, and Versailles.

At the first French census in 1801, Seine-et-Oise had 421,535 inhabitants. With the growth of the Paris suburbs, the population of Seine-et-Oise increased markedly, and by 1968 it had reached 2,943,350 inhabitants. It was judged that Seine-et-Oise, along with several other departments in the Paris conurbation, was now too large and ungovernable. On 1 January 1968 it was split into (essentially) three smaller départements: Yvelines, Val-d'Oise, and Essonne. A small part of Seine-et-Oise was also merged with parts of the Seine département (also disbanded on the same date) to create the three new départements of Hauts-de-Seine, Val-de-Marne, and Seine-Saint-Denis.

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