The history of Mexico, a country in the southern portion of North America, covers a period of more than three millennia. First populated more than 13,000 years ago, the territory had complex indigenous civilizations before being conquered by the Spanish in the 16th century. One of the important aspects of Mesoamerican civilizations was their development of a form of writing, so that Mexico's written history stretches back hundreds of years before the arrival of the Spaniards in 1519.