In the United States, heat waves are responsible for more deaths than floods, tornadoes, and hurricanes combined, even though heat waves are predictable, and heat-related mortality is preventable. The Eastern metropolis, spanning from New York City to Wilmington, Delaware, is at particularly high risk of heat-related mortality. Despite a similar climate, heat-related mortality in the region is not uniform. Most comparative research of inter-urban variation in heat-related mortality has stopped at identifying climatic variables associated with mortality responses. Climatic conditions are the source of exposure, yet urban settlement patterns, housing stock, and demographic composition affect vulnerability to heat-related mortality. This research identifies heat/mortality responses between 1980 and 1993 for 26 U.S. counties between New York City and Wilmington.