The analysis of food residues (encrustations) on prehistoric pottery may be used to determine the general provenance and harvest location of prehistoric crops. Previous work on the analysis of prehistoric residues demonstrated that the residues are the remains of food and that there is a correlation between the elements found in experimentally produced and ancient encrustations. Our analysis of Late Woodland Iroquois and modern food residues, and of soils from western New York State, by inductively coupled plasma spectrometry (ICP) substantiates the fact that differences in chemical composition of the soils are reflected in the food residue. For most sites the trace elemental profiles of the encrustations correlated best with local crops and soils, suggesting local food production. However, at one site, residue compositions did not correlate with local soils but did correlate with soils and crops in two adjacent zones. The implication is that the food was imported to this site from the east.