Costa Rica–Nicaragua border
A line that follows the Costa Rican bank of the San Juan River, then runs straight to the Pacific. Drawn in 1858 and upheld by a US president in 1888, it has taken the two countries to the World Court again and again over dredging, a road, and a strip of beach.
Written from cited sourcesLast checked 28 September 2026Suggest a correction
See it on the globe:Costa Rica →Nicaragua →
A river that belongs to one side
Costa Rica and Nicaragua became independent from Spain on 15 September 1821 and belonged to the Federation of Central America until 1838. Their boundary was set by the Cañas–Jerez Treaty of 15 April 1858, which runs the line along the right, Costa Rican, bank of the San Juan River, keeping the river itself in Nicaragua, then round the old fort of El Castillo, parallel to the river two miles from it, and in a straight line to the centre of Salinas Bay on the Pacific.[1]
Quarrels over ports and waterways followed, sharpened by plans for an interoceanic canal along the San Juan and Lake Nicaragua. In March 1888 the US president, Grover Cleveland, upheld the 1858 treaty in an arbitral award. An American engineer, Edward P. Alexander, then settled the details in five awards between 1897 and 1900, fixing the line across the sandbar to Harbor Head Lagoon at the Caribbean end, the lake shore and the centre of Salinas Bay; pillars 2 to 20 were set from the river to the Pacific.[1]
“shall continue along the right bank of said River to a point 3 English miles from El Castillo Viejo”[1]
At the World Court
In December 2015 the International Court of Justice ruled on two joined cases. It found that Nicaragua had violated Costa Rica’s territorial sovereignty and navigational rights, but not its environmental obligations, in dredging the San Juan, and that Costa Rica had failed to carry out an environmental impact assessment for Route 1856, a road it built along the river. Both governments committed to abide by the ruling.[3]
The coast at the river mouth kept moving. On 2 February 2018 the court ruled that Costa Rica holds the whole northern part of Isla Portillos, while Harbor Head Lagoon and the sandbar in front of it are Nicaraguan, and ordered Nicaragua to remove a military camp it had set up on the beach. Because the eroding coast has no stable point, the court anchored the Caribbean sea boundary to a fixed point two nautical miles offshore, joined to the coast by a line that moves with it.[2]
Timeline
185815 April 1858
Cañas–Jerez Treaty
The boundary is set along the San Juan.[1]
1888
Cleveland award
The US president upholds the 1858 treaty.[1]
189730 September 1897
First Alexander award
The Caribbean end is fixed at Harbor Head.[1]
201516 December 2015
ICJ judgment
The court finds violations by both sides.[3]
20182 February 2018
Isla Portillos
The court rules on the beach and draws the sea boundaries.[2]
Sources
- [1]International Boundary Study No. 158: Costa Rica – Nicaragua Boundary · US Department of State, Office of the Geographer · 16 August 1976
- [2]Maritime Delimitation in the Caribbean Sea and the Pacific Ocean; Land Boundary in the Northern Part of Isla Portillos: press release 2018/9 · International Court of Justice · 2 February 2018
- [3]Ban hails commitment by Costa Rica, Nicaragua to abide by UN court’s ruling on border dispute · UN News · 17 December 2015
Map geometry from Natural Earth via world-atlas. See credits.