As a result of the passing of the Affordable Care Act (ACA), main states decided to expand Medicaid. This expansion led to millions of previously uninsured Americans gaining access to health insurance. As a result, uninsured patients’ utilization of the emergency department (ED) should have declined. There are two specific aims of this study 1) identify changes in ED utilization over time by insurance status and 2) analyze the total cost of care provided to the uninsured over time. The hypotheses are 1) ED utilization among the uninsured has declined over time and 2) the total cost of care provided to uninsured patients has declined over time. The Nationwide Emergency Department Sample from 2006-2015 will be analyzed to determine the changes in the number of uninsured using the ED and cost of care provided to the uninsured. The dependent variables include ER utilization and cost of care. The independent variables of interest include patient characteristics (insurance status, age, and gender) and hospital characteristics (size, trauma designation, control, teaching status, and region). The hospital’s region will be an important policy variable since several states in specific regions (e.g., the South and Midwest) did not expand Medicaid. Chi-square will be calculated to determine if a significant correlation exists between the dependent and independent variables. Time series analysis will allow the researchers to determine if the utilization of ED services and cost of care for the uninsured has changed over time. The results of this analysis will expand our understanding of the effectiveness of the ACA’s Medicaid expansion and other policy provisions targeting the uninsured. The results will also inform hospital administrators regarding national ED utilization and cost trends.