Partidos

A partido is the second-level administrative subdivision in the province of Buenos Aires, Argentina. They are formally considered to be a single administrative unit, and usually contain one or more population centers (i.e. towns and cities). They are divided into localidades, which correspond to the municipalities in other departments. Partidos are distinct from all other provinces of Argentina, which call their second-level subdivisions departamento, and are further subdivided into distinct municipalities.

By the end of 17th century the municipal council (cabildo) of Buenos Aires established the first partidos in the countryside: San Isidro del Pago de la Costa (San Isidro) in 1779 and San Vicente, Quilmes, Magdalena, La Matanza, Cañada de Morón (Morón), Las Conchas (Tigre) and San Pedro in 1784.

At the head of every partido, the cabildo appointed a rural judge called Alcalde de la Santa Hermandad. The judge, or alcalde, had the mission to maintain the law and order in the surrounding rural area of Buenos Aires, fighting against cattle raiders. The alcalde was helped by a constabulary called Santa Hermandad (Holy Brotherhood) created in the late 15th century by the Catholic Monarchs and transplanted to the colonies.

...
Wikipedia