The Municipality of Buin was in charge of the local administration of the department. The department government was also located in Buin. In 1891, four municipalities were established as a result of the "Decree of Creation of Municipalities": Buin, Maipo, Valdivia de Paine and Estación de Hospital (or simply Hospital). Later that decade, the municipalities of Pirque and Santa Rosa were also established, and later, Paine.
