The center of Mexico is a great, high plateau, open to the north, with mountain chains on the east and west and with ocean-front lowlands lying outside of them. The terrain and climate vary from rocky deserts in the north to tropical rain forest in the south. Mexico's major rivers include the Ro Bravo del Norte (Rio Grande) and the Usumacinta on its northern and southern borders, respectively, together with the Grijalva, Balsas, Pnuco, and Yaqui in the interior. With an estimated 2005 population of about 106.5 million, Mexico is the most populous Spanish-speaking country in the world.
On September 16, 1810, independence from Spain was declared by Miguel Hidalgo y Costilla, a Catholic priest in the small town of Dolores, causing a long war that eventually led to independence in 1821 and the creation of the First Mexican Empire. After independence, Spanish possessions in Central America which also proclaimed independence were all incorporated into Mexico from 1822 to 1823, with the exception of Chiapas. Soon after achieving its independence from Spain, the Mexican government, in an effort to populate its sparsely-settled hinterlands, awarded land grants in a remote area of the northernmost state of Coahuila y Tejas to hundreds of immigrant families from the United States, on the condition that the settlers convert to Catholicism and assume Mexican citizenship. It also forbade the importation of slaves, a condition that, like the others, was largely ignored. The Empire soon fell to rebellious republican forces led by Antonio Lpez de Santa Anna. The first Republic was formed with Guadalupe Victoria as its first president, followed in office by Santa Anna. As president, in 1834 Santa Anna abrogated the federal constitution, causing insurgencies in the southern state of Yucatn and the northernmost portion of the northern state of Coahuila y Tejas. Both areas sought independence from the Mexican government. While negotiations eventually brought Yucatn to again recognize Mexican sovereignty, Santa Anna's army turned to the northern rebellion. The inhabitants of Tejas, calling themselves Texans and led mainly by relatively recently-arrived English-speaking settlers, declared independence from Mexico at Washington-on-the-Brazos, giving birth to the Republic of Texas. Texas won its independence in 1836, further reducing the territory of the fledgling republic. In the 1840s, Mexico was invaded and defeated by the United States, which demanded and received roughly one-half of the country's remaining territory, from which were formed the modern states of California, Nevada, and Utah, and most of Arizona, New Mexico, and Colorado. The PRI governments in power for most of the 20th century had a policy of granting asylum to fellow Latin Americans fleeing political persecution in their home countries. Mexico also has a sizeable population of Asians numbering around 200,000, many of them being Chinese and Japanese. There are also a small amount of Lebanese. Mexico is the country where the greatest number of U.S citizens live outside the United States. This may be due to the growing economic and business interdependence of the two countries under NAFTA, and also that Mexico is considered an excellent choice for retirees. A clear example of the latter phenomenon is provided by San Miguel de Allende and