We use Geographic Information System tools to develop estimates of the economic impact of disaster events such as Hurricane Katrina. Our methodology relies on mapping establishments from the Census Bureau’s Business Register into damage zones defined by remote sensing information provided by FEMA. The identification of damaged establishments by precisely locating them on a map provides a far more accurate characterization of affected businesses than those typically reported from readily available county level data. The need for prompt estimates is critical since they are more valuable the sooner they are released after a catastrophic event. Our methodology is based on pre-storm data. Therefore, estimates can be made available very quickly to inform the public as well as policy makers. Robustness tests using data from after the storms indicate our GIS estimates, while much smaller than those based on publicly available county-level data, still overstate actual observed losses. We discuss ways to refine and augment the GIS approach to provide even more accurate estimates of the impact of disasters on businesses.