Human activities are often arranged into zones or groups. For example, a town may have a central business district, residential areas, schools, medical clinics, etc. Activity patterns are determined in part by the basic layout. In contrast, a manufacturing plant is designed to have an assembly line or assembly areas, parts fabrication, inventory storage, etc. The layout of any facility helps determine the cost of manufacturing a product, just as the layout of a town helps determine the extent to which various people travel to accomplish daily tasks. The layout or location of all or a subset of such activities is called spatial optimization. This review article describes a number of different spatial optimization problems and concludes with directions for future research.