It is partly within two of Mexico's Biosphere Reserves, featuring a number of important species, including the horned guan (Oreophasis derbianus), Baird's tapir (Tapirus bairdii), the Jaguar (Panthera once) and rare cloud forest and mangrove habitat.

[3] Mapastepec was upgraded to the status of town (villa) by a decree issued by Ephraim A. Osorio, then governor of the State of Chiapas, on July 5, 1955.

[3] The total population of the municipality was 47,932 at the time of the 2015 Intercensal Survey, conducted by the National Institute of Statistics and Geography (Instituto Nacional de Estadística y Geografía - INEGI).

Isolation and the poor condition of roads, particularly at higher altitudes, makes access to public services difficult for many of the smaller settlements.

It is bounded by the municipalities of La Concordia, Ángel Albino Corzo and Montecristo de Guerrero to the north, Siltepec, Acacoyagua and Acapetahua to the east, the Pacific Ocean to the south, and Pijijiapan to the west.

It stretches from the Pacific Ocean to the Sierra Madre de Chiapas mountain range, with a maximum altitude of 2,700 m (8,900 ft) above sea level (a.s.l.).

The Pico El Loro-Paxtal ecological conservation zone was created by decree of November 22, 2000 to protect cloud forest in the Sierra Madre de Chiapas foothills.

It contains two of the most endangered ecosystems in Mexico: the Soconusco tropical rainforest, and cloud forest growing to over 2,000 meters (6,600 ft) above sea level.

Located to the south of the town of Mapastepec, La Encrucijada contains one of the most significant wetland and coastal lagoon networks in Mexico, with mangroves among the tallest of the Pacific coast of the Americas.

[10][7] Both the El Triunfo and La Encrucijada Biosphere Reserves are under the administration of the National Commission of Protected Natural Areas (Comisión Nacional de Áreas Naturales Protegidas, CONANP), an agency of the Federal government.

[11] The vegetation of Mapastepec varies from the lowland jungle and mangroves of the Pacific coastal plain to oak–pine forest in the high mountains of the Sierra Madre de Chiapas.

The endangered horned guan (pavón cornudo; Oreophasis derbianus), considered the state bird, is found in El Triunfo Biosphere Reserve in the high mountains of Mapastepec and neighboring municipalities.

Other key species include Azure-rumped tanager (Poecilostreptus cabanisi), the king vulture (Sarcoramphus papa), Baird's tapir (Tapirus bairdii); the Jaguar (Panthera once), the oncilla (Leopardus tigrinus) and the otter (Lutrinae).

[13] Also found are hummingbirds, the harpy eagle, hawk, parrot, owl, skylark, chupamiel, mockingbird, rook, buzzard, pigeons, doves, yellow-throated toucans and many other bird species.

[12] Also endemic to the area are the cinnamon-tailed sparrow (Peucaea sumichrasti), berylline hummingbird (Amazilia berillyna), green-fronted hummingbird (Amazilia viridifrons), giant wren (Campylorhynchus chiapensis), Mexican hairy dwarf porcupine (Coendou mexicanus), Mexican spiny-tailed iguana (Ctenosaura pectinata), flammulated flycatcher (Deltarhynchus flammulatus), Red-breasted chat (Granatellus venustus), West Mexican chachalaca (Ortalis poliocephala), rose-bellied bunting (Passerina rositae), longtail spiny lizard (Sceloporus siniferus), citreoline trogon (Trogon citreolus), Sonora mud turtle (Kinosternon sonoriense), and the cinnamon myotis bat (Myotis fortidens).

Heavy exploitation over many years, in particular of timber, has led to significant deforestation in the municipality, causing species loss and environmental degradation.

[7] Typical dishes of the municipality are iguana tamales, armadillo stew, baked chicken, marshmallow candies, nuegados chilacayote, coconut water, beer, cocoa, and white pozol.

[17] The economy of the municipality is based on agriculture, beef and dairy cattle and other livestock farming, fishing and aquaculture, forestry and construction, tourism, trade and services.

[8][7] Approximately half of the municipality lies on the Pacific coastal plain, facilitating extensive agriculture and allowing for significant mechanization.

These include public transportation, gas and service stations, hotels and restaurants, garages and repair shops, a hospital, clinics, and medical professionals.

[7] The town Mapastepec has a Rural Hospital with a number of medical units run by the Mexican Social Security Institute (Instituto Mexicano del Seguro Social, IMSS)[19] under its IMSS Prospera program[20] Health services provided include an emergency department, surgical facilities, a labor ward, a pediatrics department, a general hospital and laboratory services.

Work began in 1902 with initial repairs to a short existing rail segment from the port town of Puerto Arista on the northern coast of Chiapas in 1902.