Campeche (), officially the Free and Sovereign State of Campeche (), is one of the 31 states which make up the 32 Federal Entities of Mexico. Located in southeast Mexico, it is bordered by the states of Tabasco to the southwest, Yucatán to the northeast, and Quintana Roo to the east; to the southeast by the Orange Walk district of Belize, and by the Petén department of Guatemala to the south. It has a coastline to the west with the Gulf of Mexico. The state capital, also called Campeche, was declared a World Heritage Site in 1997. The formation of the state began with the city, which was founded in 1540 as the Spanish began the conquest of the Yucatán Peninsula. The city was a rich and important port during the colonial period, but it declined after Mexico's independence. Campeche was part of the province of Yucatán but split off in the mid-19th century, mostly due to political friction with the city of Mérida. Much of the state's recent economic revival is due to the discovery of petroleum offshore in the 1970s, which has made the coastal cities of Campeche and Ciudad del Carmen important economic centers. The state has important Mayan and colonial sites; however, these are not as well-known or visited as others in the Yucatán.