Mexico, (pronounced i /'m?ks?ko?/; Spanish: México ['mexiko]), officially known as the United Mexican States (Spanish: Estados Unidos Mexicanos), is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of Mexico. Covering almost 2 million square kilometres (over 760,000 sq mi), Mexico is the fifth-largest country in the Americas by total area and the 14th largest independent nation in the world. With an estimated population of 111 million, it is the 11th most populous country and the most populous Hispanophone country on Earth. Mexico is a federation comprising thirty-one states and a Federal District, the capital city. In Pre-Columbian Mesoamerica many cultures matured into advanced civilizations such as the Olmec, the Toltec, the Teotihuacan, the Zapotec, the Maya and the Aztec before the first contact with Europeans. In 1521, Spain conquered and colonized the territory, which was administered as the Viceroyalty of New Spain. This territory would eventually become Mexico as the colony independence was recognized in 1821. The post-independence period was characterized by economic instability, the Mexican–American War and territorial cession to the US, a civil war, two empires and a domestic dictatorship. The latter led to the Mexican Revolution in 1910, which culminated with the promulgation of the 1917 Constitution and the emergence of the country's current political system. Elections held in July 2000 marked the first time that an opposition party won the presidency from the Institutional Revolutionary Party (Spanish: Partido Revolucionario Institucional, PRI). After rapid economic, social and technological growth beginning in the 1990s, Mexico is now both one of the world's largest economies and one of the fastest growing economies in the world, with a stable growth rate of 7.6%. As a regional power, and since 1994 the first Latin American member of the Organisation for Economic Co-operation and Development (OECD), Mexico was firmly established as an upper middle-income country, and in 2009 Mexico surpassed the world bank's high income economic threshold to become a high income country. Mexico is considered a newly industrialized country and an emerging power. It has the 13th largest nominal GDP and the 11th largest by purchasing power parity. The economy is strongly linked to those of its North American Free Trade Agreement (NAFTA) partners, especially the United States, as well as tourism, being the world's tenth most visited country with over 21.4 million international arrivals. Mexico boasts a long tradition in the arts, renowned cuisine, and culture, and it ranks fifth in the world and first in the Americas on the list of UNESCO World Heritage Sites with 31.