Explores a potential indicator of EMS availability, the Expected Annual Emergency Miles per Ambulance (EXAMB). The ambulance is used as the core unit of availability due to its importance for safe transport and the initiation of medical services. The EXAMB measure calculates expected annual emergency miles per ambulance beginning with the number of ambulances, the land area of a county as a proxy for distance, and county population. Findings showed that in three of the five states studied, EXAMB values varied in parallel with other measures of resource availability, and in all states, the EXAMB was positively related to the proportion of the county population in poverty.