When a major hazard event occurs, it is often difficult to ascertain quickly what the degree of population exposure might be, and what major infrastructure might be affected by the event. NASA's Socioeconomic Data and Applications Center (SEDAC) Hazards Mapper provides a simple, online tool for estimating the population in proximity to a hazardous event and for identifying nearby facilities, including major dams, nuclear power plants, and settlements. The Mapper also displays near real-time data on earthquakes, fires, air quality, and, for the U.S., flood and tornado warnings.