Islas Marías, UNESCO Biosphere Reserve archipelago near San Blas, Mexico
Islas Marías is a four-island archipelago in the Pacific Ocean, located 100 kilometers off the coast of Nayarit and 370 kilometers from the Baja California peninsula. The largest island, María Madre, served as a federal penal colony until 2019 and now forms part of a UNESCO Biosphere Reserve.
The Mexican government established a federal prison on María Madre in 1905, housing inmates in remote isolation. The facility remained operational for over a century until President Andrés Manuel López Obrador ordered its closure in 2019.
The former penal colony on María Madre houses murals painted by inmates during their time there, showing scenes from prison life. These works remain visible today, documenting life and labor in the colony across more than a century.
Ferry services depart weekly from San Blas and Mazatlán, allowing limited visits to the archipelago with government authorization. The crossing takes several hours across open ocean, so travelers should prepare for changing conditions.
The Salera Salt Mines on María Madre still show buildings and tools from the time when inmates extracted salt there. Remnants of their murals remain visible within these facilities, showing an unusual link between forced labor and artistic expression.
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