The international border between Bolivia and Chile runs for about along the Cordillera Occidental on the western edge of the Altiplano Plateau. The line was fixed by the 1904 Treaty of Peace and Friendship, which followed the War of the Pacific, in which Bolivia lost its coastline and became landlocked. Indigenous Aymara communities live on both sides of the boundary.

The border is central to a long-running dispute between the two countries over Bolivia's demand for sovereign access to the Pacific Ocean. The International Court of Justice (ICJ) found in 2018 that Chile had no legal obligation to negotiate such access. The two states have had no ambassador-level relations since 1978, although they maintain consulates and have moved toward closer ties since 2025. A second dispute, over the status and use of the waters of the Silala River, was taken to the ICJ by Chile in 2016 and resolved largely by the parties' agreement in a 2022 judgment.

Since 2021 the border has also been a major point of entry for irregular migrants, mostly Venezuelans, entering northern Chile, which has put heavy pressure on the small border town of Colchane. In response Chile has expanded military patrols and, since March 2026, has dug trenches along parts of the frontier.

Geography

The boundary follows high Andean terrain, much of it volcanic. The World Factbook notes active volcanism along the border, including Irruputuncu (5,163 m), which last erupted in 1995, and the Olca-Paruma complex. Colchane, the principal Chilean settlement at the main crossing, lies at about 3,700 meters (12,100 ft) above sea level.

Aymara communities live on both sides of the border. A study of the Colchane–Pisiga crossing found that people recognized as Aymara were generally allowed to cross, while Caribbean migrants met stricter and more variable controls.

History

Origins of the boundary The first boundary treaty between Chile and Bolivia was signed on 10 August 1866. The line in the Atacama region was overturned by the War of the Pacific, which began in 1879; Bolivia was militarily overwhelmed and withdrew from the fighting, leaving Chile and Peru as the main combatants. A truce convention was signed on 4 April 1884.

1904 treaty The Treaty of Peace and Friendship was signed in Santiago on 20 October 1904. It recognized Chile's perpetual sovereignty over the territories it had occupied and set the boundary from south to north. It also provided for engineers to demarcate the line, with disputes to be referred to the German emperor. According to AFP reporting, Bolivia ceded about 120,000 km2 and 400 km of Pacific coast. In return it received a payment of £300,000 and free transit through Chilean ports. Chile also agreed to finance a railway between Arica and La Paz.

Bolivian governments have long contested the treaty's legitimacy and its implementation. In 2011 President Evo Morales called the treaty unjust and said Chile had not fulfilled it. Chilean President Sebastián Piñera said dialogue should take place within the framework of the treaty.

Diplomatic ruptures The two states broke relations in 1962 after Bolivia accused Chile of diverting the waters of the Lauca River. Relations were restored after Presidents of both countries signed the Charaña Joint Declaration on 8 February 1975, but the break was reinstated in 1978. Since then the countries have kept consulates general in La Paz and Santiago but no ambassadors.

Maritime claim and the 2018 ICJ judgment In 2006 the two governments agreed a 13-point bilateral agenda that included a "maritime issue". Bolivia later filed a case at the ICJ seeking a declaration that Chile was obliged to negotiate sovereign access to the Pacific. On 1 October 2018 the court ruled, by twelve votes to three, that Chile had not undertaken such an obligation. It added that the ruling did not preclude the parties from continuing their dialogue.

Rapprochement since 2025 Rodrigo Paz, who became Bolivia's president in November 2025, and José Antonio Kast, who took office in Chile on 11 March 2026, have both sought to improve relations. The foreign ministers of both countries met at the Chungará–Tambo Quemado crossing on 23 April 2026 before continuing to La Paz, and signed an air services agreement. Bolivian officials have said the new approach does not mean abandoning the maritime claim. In September 2026 a delegation of the Chilean Senate's foreign affairs committee visited La Paz, with border security and migration on the agenda. Bolivia's foreign minister said that a possible visit by Kast in October would be an important step.

Border crossings The main crossings are Visviri–Charaña, Chungará–Tambo Quemado, Colchane–Pisiga, Ollagüe–Abaroa and Hito Cajón–Cajones. The two countries coordinate border management through a bilateral Border and Integration Committee. Land crossings closed during the COVID-19 pandemic and reopened to passenger traffic on 1 May 2022. In August 2026 Chile's border crossings unit reported that Chungará and Colchane were open 24 hours, Visviri from 08:30 to 20:00, and Ollagüe and Hito Cajón from 08:00 to 18:00.

Silala River dispute

The Silala River rises from groundwater springs in Bolivia's Potosí Department, 0.5 to 3 kilometers north-east of the boundary at about 4,300 meters. It flows across the border into Chile's Antofagasta Region and joins the San Pedro River about 6 kilometers beyond the boundary. Its use began in 1906, when a railway company, the Antofagasta (Chili) and Bolivia Railway Company, obtained a Chilean concession to increase the drinking water supply of Antofagasta. In 1908 the same company obtained a Bolivian right of use to supply locomotives. It built channels in Bolivia in 1928. Chile says these were for sanitary purposes, while Bolivia says they artificially enhanced the flow into Chile. Before the litigation, scholars had described the basin as vulnerable to conflict and a possible catalyst for cooperation.

Bolivian authorities revoked the railway company's concession in May 1997, and by 1999 the status of the river was disputed between the two governments. Chile instituted proceedings at the ICJ on 6 June 2016, after Morales said the Silala was not an international river and accused Chile of using its waters without compensation.

In its judgment of 1 December 2022 the court found that most of the claims and counter-claims of both sides no longer had any object. During the proceedings Bolivia had come to accept that the Silala is an international watercourse governed in its entirety by customary international law, and the parties agreed that both are entitled to equitable and reasonable use of its waters. They also agreed that it is within Bolivia's sovereign powers to dismantle the channels in its territory. The court unanimously rejected Chile's claim that Bolivia had breached an obligation to notify and consult, and unanimously rejected Bolivia's third counter-claim, which concerned a hypothetical future delivery of enhanced flow to Chile. Judge Peter Tomka observed in a declaration that the judgment decided almost nothing, and ad hoc judge Bruno Simma expressed reluctance about the approach taken. The court invited the parties to continue consultations in a spirit of cooperation.

Landmines Chile laid antipersonnel mines along its borders in the 1970s under the Pinochet dictatorship, including 22,988 on the Bolivian frontier according to a Chilean consul in 2010. Clearance began at Chungará–Tambo Quemado in July 2005 under the Ottawa Treaty. In 2015 Bolivia accused Chile of failing to meet its obligations, which Chile rejected, saying it had an extension until 1 March 2020. Chile has been officially considered cleared since 2020, although a former head of its demining commission has said some residual risk remains.

Migration and border security Irregular migration since 2021 Since 2021 the Bolivia–Chile border has been a major point of entry for irregular Venezuelan migrants into Chile. Migrants are aided in the crossing by human smugglers. Irregular migration has been particularly troublesome for the Chilean border town of Colchane, which has about 1,600 inhabitants and a primary health system able to treat only a few people at a time. In February 2021 the mayor of Colchane said that some arrivals had entered homes and assaulted residents.

In March 2022, Chile's Investigative Police recorded 3,213 people entering through unofficial crossing points, and seven deaths of migrants had been registered at Colchane in 2022 by the end of that month. The mayor said that maintaining existing border ditches and a constitutional state of exception had cut daily arrivals from 500–600 in January to about 300. Nationally, irregular entries fell by 5 percent in 2022, from 56,586 to 53,875, but entries into the Tarapacá Region rose by 19 percent. In early 2023 Chile deployed troops at critical points on its borders with Peru and Bolivia for 90 days. Chile's migration service reported 21 percent fewer irregular entries in 2023, with fewer Venezuelans and more Bolivians crossing at Colchane. The mayor of Colchane has said that irregular crossings will continue as long as Bolivia does not agree to readmit irregular migrants.

Border Shield plan The Kast government launched the "Escudo Fronterizo" (Border Shield) plan to curb irregular migration and transnational crime and to channel movement through authorized crossings. Work on trenches and walls began on 16 March 2026 at Chacalluta on the Peruvian border and at Colchane on the Bolivian border. Defense Minister Fernando Barros said that the plan was not intended to militarize the border. Authorities estimated that about 120,000 stolen or undocumented vehicles enter Bolivia each year from northern Chile along clandestine routes. The Ministry of Public Works said the army-supported works were meant to impede cars and trucks. By May 2026 two ditches were being dug along the Bolivian border, and two Bolivian citizens had been detained for trying to fill in a section. Critics doubted that trenches along short stretches of the frontier would significantly reduce migration, drug trafficking or contraband.

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