Objectives To determine how frequently patients revisit the emergency department after an initial encounter, and to describe revisit capture rates for the same hospital, health system, and geographic region. Data Sources/Study Setting Florida state data from January 1, 2010, to June 30, 2011, from the Healthcare Cost and Utilization Project. Study Design This is a retrospective cohort study of emergency department return visits among Florida adults over an 18‐month period. We evaluated pairs of index and 30‐day return emergency department visits and compared capture rates for hospital, health system, and geographic units. Data Collection/Extraction Methods Data were obtained from the Agency for Healthcare Research and Quality's Healthcare Cost and Utilization Project and the American Hospital Association Annual Survey Database. Principal Findings Among 9,416,212 emergency department visits, 22.6 percent (2,124,441) were associated with a 30‐day return. Seventy percent (1,477,772) of 30‐day returns occurred to the same hospital. The 30‐day return capture rates were highest within the same geographic area: county‐level capture at 92 percent (IQR=86–96 percent) versus health system capture at 75 percent (IQR = 68–81 percent). Conclusions Acute care utilization patterns are often independent of health system boundaries. Current population‐based health care models that attribute patients to a single provider or health system may be strengthened by considering geographic patterns of acute care utilization.