The Postclassic period of Mexico overlaps the chronological periods of Pueblo II to Pueblo IV in the Southwest US (ad 900–1600). Prior to the Postclassic period, ancestral Puebloan, Hohokam and Mogollon populations primarily occupied the Southwest US. From around ad 850–1130, Chaco Canyon was one of the largest Pueblo sites in the region. Chaco was likely an economic centre for distributing agricultural and luxury goods for the entire San Juan Basin region of Northwest Mexico (Washburn et al., 2011; Crown, 2013). Cacao from the Gulf Coast or Southern Mexico was among the items used and likely traded at Chaco Canyon (Crown and Hurst, 2009). Between ad 1130 and 1180, coinciding with a period of disastrous drought, Chaco Canyon was abandoned, and migrants dispersed south into the Rio Grande Valley and Northern Mexico (Benson et al., 2007). These migrations likely led to population growth and the development of a large inter-regional trade centre at Casas Grandes in Northern Mexico (Kelley, 1993; Lekson, 1999). In the Southwest US, the frequency of hostile interactions increased with time (LeBlanc, 1999; VanPool and O'Brien, 2013). Economic and political relationships shifted often in response to access to resources, population growth and natural phenomena. During the Postclassic period, sites such as Hawiku in the Cibola area and Puye on the Pajarito Plateau were primarily local distribution centres. Some exotic trade items found in these areas were obtained from as far as Northern Mexico (Mills, 1995; Walsh, 2000), and Hawiku likely was involved in the trade of items from West Mexico (Riley, 1975). Hawiku, also participated in inter-group warfare, especially with Hopi and Acoma groups around the region (Hammond and Rey, 1940; LeBlanc, 1999); other hostile interactions within the Rio Grande Valley are not as well understood. Warfare on the Pajarito Plateau area declined as the pueblos grew after about ad 1400 (LeBlanc, 1999, 2000), and it is unlikely that these groups had hostile interactions with the Zuni or Hopi groups to the west. Most of the Pajarito Plateau was abandoned around the time of European contact, and occupation of the Zuni site of Hawiku continued until shortly after the Pueblo Revolt in ad 1680.
Much of Northern Mexico is often referred to as the ‘Greater Southwest’. Among the populations that occupied this region were the semi-nomadic Chichimecs, who appear in the archaeological record during the Late Postclassic period (around ad 1200). The term Chichimec does not only imply a particular ethnic, linguistic or technological identity but also refers to a large number of nomadic groups that inhabited Northern Mexico, the Gulf Coast and parts of Central Mexico (Lopéz Austin and Lopéz Luján, 2008). The Coahuilan groups in the northeast occupied caves and open areas that had access to water and desert plains (Turpin, 1997). To the northwest, the Casas Grandes culture, centred at Paquimé, controlled a large trade centre between the Southwest US and Mexico (DiPeso, 1974; Woosley and Olinger, 1993). Casas Grandes grew from a small agricultural community to a large trade centre shortly after the abandonment of Chaco Canyon, leading some archaeologists to attribute this demographic growth to ancestral Puebloan migrants (Lekson, 1999). Others argue that this growth was caused by migrants from and trade with Central Mexico (DiPeso, 1974; Nelson, 1986; Kelley, 1993). The Casas Grandes culture and its remnants throughout the region actively participated in trade and continuous inter-group warfare. Areas such as Copper Canyon in the Sierra Madre Occidental Mountains were inhabited by nomadic groups that lived in temporary cave dwellings. Many burials found in caves in this area show signs of trauma to the skeleton (Walker, 2006), and historical accounts from Spanish invaders in the 17th century describe hostile relationships between indigenous groups throughout the region. These groups were located near major trade routes along the northwestern mountains and coast of Mexico (Weigand, 2008). In general, groups from Northern Mexico were highly involved in economic and hostile interactions between the Southwest US and Mexico.