The Xochicalco archaeological site is located on hilltops in a region with difficult access. From 1992 - 1994 a major campaign, the Xochicalco Archaeological Special Project, was financed by the National Institute for Anthropology and History (INAH). Xochicalco was designated an Archaeological Monuments Zone by Federal Decree on 18 February 1994. Most of the archaeological zone is national property. The 1995 Morelos State and Municipal Urban Development Programme established regulations to control unauthorized settlement in ecological protection areas, of which the Xochicalco Archaeological Zone is one.