The article deals with the history of Algeria's administrative divisions in the 19th and 20th century (until 1962). After the French invasion of 1830, which inaugurated 132 years of colonial rule, the territory of northern Algeria was occupied by French troops and found itself under military administration. In 1834, when Algeria was officially proclaimed French territory, the military and the civil administrations were separated. Even then, however, the colony was ruled by the military governor. The administration was divided between tribal territories and 'arrondissements', which continued with some modification, until the 20th century. The structure of city administration with mayors and city councils was based on the French metropolitan model. In 1833 the first 'Bureaux Arabes' manned by both Europeans and Arabs, were set up to take charge of the indigenous population.In 1845 it was partly demilitarized and granted more autonomy. Algeria was divided into three provinces (Algiers, Oran and Constantine), which comprised three types of territories, civil (where the Europeans formed a majority), military (with indigenous population), and mixed (also run by the military, in areas with a small European population). Later the military territories were reclassified as mixed, and the mixed ones were granted full civil status. In 1848 the three provinces were refashioned into departements, subdivided into arrondissements and communes. In 1870, by special decree, Algeria was joined to France. Administratively, it consisted of three departements incorporating the former civil and military units. In the north the four-tier structure - with 3 departements, 20 arrondissements, 330 autonomous communes and 78 mixed communes - remained virtually unaltered until 1955. In 1958 in a major decentralizing reform, three new departements were created, while the old ones were divided into five territoires each. The arrondissements were reclassified as communes. This division was replaced by a new administrative grid in 1962, when Algeria became independent..