In the aftermath of the September 11 terrorist attacks, the United States established state and local fusion centers to strengthen domestic intelligence capabilities and promote information sharing among intelligence and law enforcement agencies, aiming at detecting, preventing, investigating, and responding to criminal and terrorist activities. This paper discusses the adjustment of the U.S. domestic intelligence strategy, explains the creation and development of fusion centers and their operations, summarizes reviews and performance evaluations conducted by various institutions, and finally lists lessons learned from the practice of fusion centers.