The Treaty of Ancón was signed by Chile and Peru on October 20, 1883, in the Ancón District near Lima. It was intended to settle the two nations' remaining territorial differences at the conclusion of their involvement in the War of the Pacific and to stabilise post-bellum relations between them.
Under the treaty's terms, Chile gained control over Tarapacá. Chile also got Tacna and Arica for ten years.
Another important chapter in the treaty said that Chile could not cede sovereignty of former Peruvian territories to other nations without asking Peru first. The Chapter have been invoked once, during the Chilean proposal of 1975 that offered Bolivia sovereignty over some minor ports.