Various hospitals in the US and around the world suffer from the well-known problem of emergency department (ED) overcrowding, which prevents them from serving patients effectively and efficiently. An important contributor to this problem, which became even more dire after the COVID-19 pandemic, is prolonged boarding of patients who are admitted to inpatient units through the ED. Patients admitted through the ED constitute about 50% of all nonobstetrical hospital admissions in the US, and they may be boarded in the ED for long hours with the hope of finding an available bed in their primary inpatient unit. This chapter sheds light on effective ways of reducing ED boarding times by considering the trade-off between keeping patients in the ED and assigning them to a secondary inpatient unit. Using simulation analyses calibrated with hospital data, they find that implementing this policy could significantly help hospitals to improve their patient safety by reducing boarding times while controlling the overflow of patients to secondary units. Using data analyses and various simulation experiments, they also help hospital administrators by generating insights into hospital conditions under which achievable improvements are significant.