The island lies between the San Juan (to the north and west), the Río Colorado of Costa Rica (to the south and southeast), and the Caribbean Sea (to the east and northeast).

[1][2] At that time, a territorial dispute between the two Central American nations dating back to 1850 resurfaced over an area about 3 km in length on Isla Portillos, alternatively identified by the Nicaraguans as Harbour Head Island.

The 1858 Cañas–Jerez Treaty established Nicaraguan ownership of the San Juan River but gave Costa Rica the right to navigation for commercial purposes.

[1] In December 2010, commander Edén Pastora defended the claim by citing Google Maps as a source that supported the Nicaraguan position.

[3] In March 2011, the International Court of Justice provisionally ruled that Costa Rica and Nicaragua both must refrain from sending or maintaining civilians, security forces or police in the disputed border area, but that Costa Rica was allowed to send civilian teams concerned with environmental matters.