Emergency Departments (EDs) face significant challenges in providing efficient, quality, safe, cost-effective care. Lean methodologies are a proposed framework to redesign ED practices and processes to meet these challenges. We outline a systematic way that lean principles can be applied across the entire ED patient experience to transform a high volume ED in a safety net hospital. We review the change in ED performance metrics prior to and after lean implementation. We discuss critical insights and key lessons learned from our lean transformation to date. The steps to implementing lean principles across the patient's ED experience are described with specific attention to executive planning of rapid improvement experiments and the subsequent roll-out of lean transformation over an 18-month time frame. Basic ED performance data were compared to the year prior. Results of the exploratory analysis (using median and interquartile ranges and nonparametric tests for group comparisons) have shown improvement in several performance metrics after initiating lean transformation. The approach, lessons learned, and early data of our transformation can provide critical insights for EDs seeking to incorporate continuous improvement strategies. Key lessons and unique challenges encountered in safety net hospitals are discussed.