Islas Marías
Former penal colony and UNESCO biosphere reserve in Mexico.
The Islas Marías ("Mary Islands") are an archipelago in the Pacific Ocean, about 100 km off the coast of Nayarit, Mexico. Comprising four principal islands and five smaller islands or large offshore rocks, they were used as a federal penal colony from 1905 until its closure on February 18, 2019, by order of President Andrés Manuel López Obrador. The islands were designated a UNESCO Biosphere Reserve in 2010 and opened to tourism in 2024.
- Location
- Pacific Ocean, 100 km off Nayarit, Mexico
- Area
- 244.97 km²
- Population
- 1,116 (2005 census, Isla María Madre) plus ~8,000 prisoners
- First european encounter
- 1532 by Diego Hurtado de Mendoza
- Penal colony established
- 1905
- Penal colony closed
- February 18, 2019
- Unesco designation
- 2010 (Biosphere Reserve)
Lore & Background
The first European to encounter the islands was Diego Hurtado de Mendoza, a cousin of Hernán Cortés, in 1532; he named them Islas Magdalenas and found no evidence of prior Native American habitation. The four main islands—Isla María Madre, Isla María Magdalena, Isla María Cleofas, and San Juanito—were named after three women called Mary in the New Testament. The archipelago is part of the municipality of San Blas, Nayarit.
The Islas Marías Federal Prison was established on Isla María Madre in 1905 under President Porfirio Díaz, who decreed the islands a penal colony. Notable prisoner José Revueltas wrote his first book, *Los Muros de Agua*, while incarcerated there. The penal colony operated continuously until its closure on February 18, 2019. In 2024, the Mexican government opened the islands to tourism for the first time.
Reader's Guide
The Islas Marías hold significance as a former penal colony that operated for over a century, reflecting Mexico's penal history under Porfirio Díaz and later administrations. The closure in 2019 marked the end of one of Latin America's last island penal colonies. Ecologically, the archipelago is a UNESCO Biosphere Reserve, hosting endemic species such as the Tres Marías amazon, Tres Marías hummingbird, Tres Marías island mouse, and the Tres Marías raccoon. Geologically, the islands are fragments of continental crust left from the separation of Baja California from mainland Mexico. The opening to tourism in 2024 aims to transform the islands into a bio-tourism destination, leveraging their unique biodiversity and historical legacy.
Did You Know?
- Hurricane Willa passed directly over the Islas Marías on October 23, 2018, with sustained winds of 88 mph and gusts to 112 mph.
- The islands' lighthouse on Isla María Madre is 62 meters tall, made of concrete, and flashes two white lights every 10 seconds.
- The main settlement, Puerto Balleto, had a population of 602 as of the 2005 census.
- The islands were named after three Marys from the New Testament: Mary mother of Jesus, Mary Magdalene, and Mary wife of Cleopas.
Frequently Asked Questions
What are Islas Marías?
Islas Marías is a small Pacific archipelago consisting of four main islands and five smaller islets or rocky outcrops. It is best known for having operated as a federal prison colony for over a century before being recognized as a UNESCO Biosphere Reserve.
Where exactly are Islas Marías located?
The islands sit roughly 100 kilometers offshore from the state of Nayarit on Mexico's Pacific coast. The entire archipelago covers about 245 square kilometers of land.
Why was Islas Marías used as a prison?
In 1905 the Mexican federal government converted the remote islands into a penal colony, exploiting their isolation to house up to around 8,000 inmates at peak capacity. The site kept functioning in that role for more than 110 years.
When did the Islas Marías prison close?
President Andrés Manuel López Obrador signed the order shutting down the penal colony on February 18, 2019. Following that closure the islands gradually shifted toward conservation and regulated public access.
Can tourists visit Islas Marías today?
Yes—the archipelago was officially opened to tourism in 2024 after receiving its UNESCO Biosphere Reserve designation in 2010. Access is still managed to protect the local ecosystem, but visitors can now explore the islands.
More in World Heritage Sites in Mexico 1-24
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