The large public plazas of the ancient Maya were likely swept clear of debris and durable artifacts that could have provided evidence of the ancient anthropogenic activities. However, geochemical residues of food or mineral ores and pigments became affixed to soil and floor particles. These particles chemically bound so that natural movement of water is insufficient to cause them to move, leaving invisible geochemical signatures of ancient activities. This line of study is focused on the relationship between the geospatial distribution of element concentrations and ancient human activities using current laboratory techniques and isopleths, or chemical concentration contour maps, to identify activity areas. Surface samples were collected from ancient plazas at the sites of Kiuic and Sayil in the Puuc Hills of Yucatan and at the site of Caracol Belize. Mehlich II and DTPA extraction procedures were used to determine the elemental concentrations of P, Cu, Fe, Mn, Pb, and Zn. Total elemental levels of additional elements were determined by portable X-ray fluorescence. The objective was to discover geochemical evidence of economic exchange activities at these important site centers. The Kuche Plaza at Kiuic produced evidence of ancient food storage, consumption, or trade activities but such evidence was lacking from the largest open space at the site. The Mirador group at Sayil failed to produce compelling evidence of any market activities. In the Conchita plaza at Caracol there are significant chemical signatures of human activities including evidence of ancient food storage, consumption, or trade activities and evidence of workshop activities potentially including the use production or trade of pigments. Our results from the Conchita plaza suggest ancient marketplace activity, and a geospatial division for the use of the Conchita plaza at Caracol.