This article is about the country in North America. For other uses, see Mexico (disambiguation). Coordinates: 23°N 102°W / 23°N 102°W / 23; -102 Mexico (/ˈmɛksɪkoʊ/; MEK-si-koh; Spanish: México, pronounced [ˈmexiko] ( listen)), officially the United Mexican States (Spanish: Estados Unidos Mexicanos, listen (help·info)), is a federal republic in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatemala, Belize, and the Caribbean Sea; and to the east by the Gulf of Mexico. Covering almost two million square kilometers (over 760,000 sq mi), the nation is the sixth largest country in the Americas by total area and the 13th largest independent state in the world. With an estimated population of over 120 million, the country is the eleventh most populous and the most populous Spanish-speaking state in the world while being the second most populous nation in Latin America. Mexico is a federation comprising 31 states and a special federal entity that is also its capital and most populous city. Other metropolises include Guadalajara, León, Monterrey, Puebla, Toluca, and Tijuana. Pre-Columbian Mexico dates to approximately 8,000 BCE, is identified as one of seven cradles of civilization and was home to many advanced Mesoamerican civilizations, such as the Olmec, Toltec, Teotihuacan, Zapotec, Maya and Aztec before first contact with Europeans. In 1521, the Spanish Empire conquered and colonized the territory from its politically powerful base in Mexico-Tenochtitlan, which was administered as the viceroyalty of New Spain. Three centuries later, the territory became the current nation following recognition in 1821 after the colony's Mexican War of Independence. The tumultuous post-independence period was characterized by economic inequality and many political deep changes. The Mexican–American War (1846–48) led to a territorial cession of the extensive northern territories to the United States. The Pastry War, the Franco-Mexican War, a civil war, two empires and a domestic dictatorship occurred through the 19th century. The dictatorship was overthrown in the Mexican Revolution of 1910, which culminated with the promulgation of the 1917 Constitution and the emergence of the country's current political system. Mexico has the fifteenth largest nominal GDP and the eleventh largest by purchasing power parity. The Mexican economy is strongly linked to those of its North American Free Trade Agreement (NAFTA) partners, especially the United States. Mexico was the first Latin American member of the Organisation for Economic Co-operation and Development (OECD), joining in 1994. It is classified as an upper-middle income country by the World Bank and a newly industrialized country by several analysts. By 2050, Mexico could become the world's fifth or seventh largest economy. The country is considered both a regional power and middle power, and is often identified as an emerging global power. Due to its rich culture and history, Mexico ranks first in the Americas and seventh in the world by number of UNESCO World Heritage Sites. Mexico is a megadiverse country, ranking fourth in the world by biodiversity. In 2016 it was the eighth most visited country in the world, with 35 million international arrivals. Mexico is a member of the United Nations, the World Trade Organization, the G8+5, the G20, the Uniting for Consensus and the Pacific Alliance.