Long before the first cell was built, indigenous groups inhabited San Lucas and the surrounding islands. Archaeologists have identified eight sites on the island, including the remains of apparent houses where stone tools and a metal object were excavated in the late 1970s. The sites date to between 1000 and 1500 AD -- centuries of habitation that left physical traces now protected alongside the prison ruins. The island's position in the gulf provided both access to fishing grounds and natural defense, qualities that would later serve very different purposes.

Tomas Miguel Guardia Gutierrez, Costa Rica's military dictator, established the prison on San Lucas in 1873. Being sent there was a sentence unto itself: prisoners' lives were short, and torture was not an aberration but a feature. The island's remoteness in the Gulf of Nicoya ensured that what happened inside its walls stayed there. For 118 years, San Lucas received some of Costa Rica's most dangerous criminals -- though the prison is often erroneously cited as the largest in the country's history. The former buildings are now designated as Patrimonio de Cultura, cultural heritage sites protected by the Costa Rican Legislative Assembly and classified as Historical-Architectural Heritage. The prison's most famous chronicler, writer Jose Leon Sanchez, was imprisoned on the island for twenty years and turned his experience into the novel La Isla de los Hombres Solos.

After the prison closed in 1991, the facilities sat abandoned. Nature reclaimed what had been cleared -- and it did so with remarkable speed. The island's isolation from mainland predators allowed wildlife populations to recover. Howler monkeys, spiders, snakes, deer, and pheasants now inhabit the interior. At least eight species of bats roost in structures that once held prisoners. The surrounding waters are home to hammerhead sharks, rays, and sea turtles. In 2002, the island was designated a protected wildlife refuge. Volunteers from the international charity Raleigh International began working with park rangers to clear beaches and improve access. In August 2020, the Costa Rican legislature voted to make San Lucas the country's 30th national park, managed under the Central Pacific Conservation Area.

San Lucas joins an unusual fraternity: island prisons turned into heritage sites and tourist destinations. Alcatraz in San Francisco Bay, Robben Island in South Africa, the Chateau d'If off Marseille, Devil's Island in French Guiana -- each shares the same geography of isolation repurposed first for punishment, then for memory. The Instituto Costarricense de Turismo has invested in developing the island's tourism infrastructure, and several companies now offer charter boats from Puntarenas. What visitors find is a place caught between its identities: archaeological site, prison ruin, wildlife sanctuary, and national park, all compressed onto a small island where the forest grows through the bars and the monkeys have taken the cells.