The Tacna–Arica compromise was a series of documents that settled the territorial dispute of both Tacna and Arica provinces of Peru and Chile respectively.
The controversy was a direct aftermath of the War of the Pacific (1879–1883), a confrontation that involved Chile against Peru and Bolivia. Chile won the war and conquered the Peruvian territories of Tarapacá, Tacna and Arica. The defeated Peruvian government was forced to sign the Treaty of Ancón in 1883.
In this Treaty, Tarapacá was annexed to Chile. However, the fate of both Tacna and Arica was to be decided by a plebiscite to be held in 1893. Due to different points of view, both countries were not able to agree on the conditions of this plebiscite. So, it was not held. Then Chile began to colonize the two territories in 1909. Peru followed in 1911 with a break of diplomatic relations. In 1922, Chile and Peru agreed to arbitrate the dispute with the President of the United States. President Coolidge appointed, in 1925, the first US arbitrator, General John J. Pershing; General William Lassiter followed in 1926. Neither negotiator was able to break the deadlock. US Secretary of State Frank B. Kellogg suggested direct negotiations in Washington, D.C. in 1928. It was these negotiations that led to the Treaty of Lima in 1929.
A deal was finally reached in 1929 in the Treaty of Lima, according to which Peru retained Tacna and Chile kept Arica. Chile had also to make some concessions such as building a Peruvian-administered wharf in Arica and a six million-dollar indemnification, among others.