History
Départements were created on January 15, 1790 by the Constituent Assembly to replace the country's former provinces with a more rational structure. They were also designed to deliberately break up France's historical regions in an attempt to erase cultural differences and build a more homogeneous nation. Most départements are named after the area's principal river(s) or other physical features.
The number of départements rose from an initial 83 to 130 by 1810 with the territorial gains of the Republic and of the Empire (see Provinces of the Netherlands for the annexed Dutch departements), but they were reduced again to 86 with Napoleon I's defeat in 1814-1815. Three more were added with the acquisition of Nice and Savoy in 1860. The numbering was estabished on the alphabetical order of those 89 départements.
Three départements in Alsace-Lorraine which had been ceded to Germany in 1871 - (Haut-Rhin, Bas-Rhin, and Moselle) - re-joined France in 1919.
Reorganisations of the Paris region (1968) and the division of Corsica (1975) have added a further seven départements, raising the total to one hundred - including the four overseas départements d'outre-mer (DOM) of Guyane (French Guiana) in South America, Guadeloupe and Martinique in the Caribbean Sea, and Réunion in the Indian Ocean.
Map and list of départements