It was ceded by the Treaty of Ancón in 1883 and placed under military administration, and then created on the 31st of October 1884, as one of the three departments of the Tacna Province, incorporating as well a disputed claim over Tarata, and was returned to Peru at midnight on the 28th of August 1929, under the terms agreed upon in the Treaty of Lima of the same year.

Its limits were defined as the Sama River to the north, the Arica Department to the south, the Andes mountain range to the east, and the Pacific Ocean to the west.

Peru, however, did not recognize this annexation on the grounds that the territory was completely unaffected by the Treaty of Ancón.

Coolidge showed himself to be in favor of the Peruvian claims on several occasions during the duration of the dispute, more so than other heads of state.

[16] Around the same time, a commission, headed by U.S. General John J. Pershing arrived to assist with the planned Tacna-Arica plebiscite, which eventually would never take place.