The prehispanic civilizations of what now is known as Mexico are usually divided in two regions: Mesoamerica, in reference to the cultural area where several complex civilizations developed before the arrival of the Spanish in the sixteenth century, and Aridoamerica (or simply "The North") in reference to the arid region north of the Tropic of Cancer where few civilizations developed and was mostly inhabited by nomadic or semi-nomadic groups. Despite the conditions however, it is argued that the Mogollon culture and Peoples successfully established population centers at Casas Grandes and Cuarenta Casas in a vast territory that encompassed northern Chihuahua state and parts of Arizona and New Mexico in the United States.