Emergency Department (ED) crowding and ambulance diversion have been increasingly significant national problems for more than a decade. Surveys of hospital directors have reported overcrowding in almost every state and 91% of hospital ED directors report overcrowding as a problem. The problem has developed because of multiple factors in the past 20 years, including a steady downsizing in hospital capacity, closures of a significant number of EDs, increased ED volume, growing numbers of uninsured, and deceased reimbursement for uncompensated care. Initial position statements from major organizations, including JCAHO and the General Accounting Office, suggested the problem of overcrowding was due to inappropriate use of emergency services by those with no urgent conditions, probably cyclical, and needed no specific policy response. More recently, the same and other organizations have more forcefully highlighted the problem of overcrowding and focused on the inability to transfer emergency patients to inpatient beds as the single most important factor contributing to ED overcrowding. This point has been further solidified by initial overcrowding research. This article will review how overcrowding occurred with a focus on the significance and potential remedies of extended boarding of admitted patients in the Emergency Department.