Coatzacoalcos (koatsakoˈalkos) is a major port city in the southern part of the Mexican state of Veracruz, mostly on the western side of the Coatzacoalcos River estuary, on the Bay of Campeche, on the southern Gulf of Mexico coast. The city serves as the municipal seat of the municipality of the same name. It is the state's third largest city, after the city of Veracruz and Xalapa. Coatzacoalcos comes from a Nahuatl word meaning "site of the Snake" or "where the snake hides." According to the legend, this is where the god Quetzalcoatl made his final journey to the sea in around 999 and he made his promise to return. Coatzacoalcos sits within the Olmec heartland. Excavations in 2008 for a tunnel under the Coatzacoalcos River indicate a substantial pre-Hispanic population. By the time of the Spanish arrival the area was under Mayan influence. In 1522, Hernán Cortés ordered Gonzalo de Sandoval to fund a settlement near Guazacualco. Sandoval named it Villa del Espíritu Santo. San Martín Tuxtla is an active volcano lying northwest of Coatzcoalcos in the Sierra de los Tuxtlas. It erupted in 1664, in May 1793 with large ash falls and lava flows, and most recently in 1796. The town was elevated to the category of port in 1825 and the name was changed to Coatzacoalcos. The municipality of Coatzacoalcos was established 22 December 1881, with the town as its seat. In 1900 the town name was changed to Puerto México. In 1911 it was elevated to city, and in 1936 the name was changed to the current Coatzacoalcos. On 23 July 1940, Coatzacoalcos welcomed refugees from the Spanish Civil War who sought asylum in Mexico after travelling across the Atlantic aboard the SS Santo Domingo. In 1959, the city suffered damage from an 6.4 earthquake. Coatzacoalcos became a very important crossroads during the oil boom of the 1970s, connecting the Yucatán Peninsula and oil fields in Campeche to the rest of Mexico and to the port of Salina Cruz in Oaxaca on the Pacific coast. The city is located at where the Coatzacoalcos River debouches into the Bay of Campeche.