The park is named for its home municipality of Mirador in central Maranhão. It covers the Serra do Itapecuru, which rises to 660 meters between the basins of the Alpercatas and Itapecuru rivers. Those rivers do not appear from nowhere. They begin here, in the springs and seeps of the serra, gathering small tributaries that eventually join into the upper Itapecuru. That river then winds north for hundreds of kilometers before emptying into the Baía de São José near São Luís. The watershed supplies water to twenty municipalities along its length. The park was meant to protect those headwaters, which means protecting the cerrado and gallery forest cover that holds the rain and releases it slowly through the year.

Vegetation here is cerrado, cerradão, and gallery forest - three related plant communities that intergrade across the landscape. A 2013 survey catalogued 140 species from 53 families. The trees run low, gnarled, and thick-barked, adapted to survive fires and long dry seasons. Among them: red and yellow ipê, arueira, cedar, and the economically valuable pau-terra. The pequi tree produces a pungent yellow fruit beloved in central Brazilian cuisine. The jatobá yields medicinal resin. Most remarkable is the fava-danta, common throughout the park, which is the commercial source of pilocarpine - an alkaloid that pharmaceutical companies turn into glaucoma medication. Along streams, large buriti palms dominate the riparian zones, their fan-shaped fronds rising above everything else. Fauna includes the endangered king vulture, giant armadillo, and bush dog, alongside Amazon parrots, margay, deer, and seriemas. Anacondas live here too.

Mirador State Park was created by decree 7.641 on June 4, 1980. The design had a problem from the start: the park was limited to the Mirador municipality alone, so surrounding municipalities had no obligation to preserve the rivers flowing through. Management fell to a department of the State Secretariat of Environment and Natural Resources, known as SEMA, which in turn outsourced the day-to-day work to a cooperative. Contracts lapsed for months or years at a time. No one monitored results. For thirty years, the park functioned mostly as a line on a map. Scientific research and ecotourism - the promised uses in the founding decree - never materialized. In November 2009 SEMA announced R$500,000 for a proper management plan involving 18 biologists, 11 researchers, and 10 coordinators from universities. The decree was adjusted by law 8.959 of May 8, 2009, and law 9.316 of December 23, 2010, formally recognized the cooperative's role.

The structural neglect had consequences. In August 2015, state deputy Rigo Teles spoke in the State Assembly after visiting the park. After the managing cooperative had stopped working, he said, widespread fires had torn through the vegetation and hunters were decimating wildlife. As of mid-2015 there were no rangers assigned. The following January, the state government announced public hearings to address concerns raised by the vice-prefect of Mirador, José Ronilde Pereira de Sousa - known locally as Rony - about environmental degradation from fires and poaching. In June 2016, SEMA technicians finally visited communities inside and near the park with environmental police and the fire department. Most residents turned out to be small farmers growing cassava and raising pigs and cattle that grazed in the park. Investigators disciplined residents suspected of holding chainsaws and seized two guns. By the end of 2012, the municipality of Mirador had passed its own law allowing it to take on joint management, believing local authorities would better spend scarce funding than the distant state government.

From a flight deck passing over central Maranhão, Mirador reveals itself as an island of relatively intact cover in a landscape that has been heavily cleared for cattle and agriculture. The Serra do Itapecuru rises as a low plateau, its edges carved by the headwater streams. Gallery forests trace every watercourse in darker green against the tan and olive tones of the cerrado. In the dry season, smoke may be visible from seasonal burning. In the wet season, the rivers swell visibly, and the buriti palms glisten in the sun. The contrast with surrounding land tells the story more honestly than any paper decree: where the park holds, the forest persists. Where it doesn't, the pasture does.