Fusion Centers are intelligence sharing and analysis hubs which tie local collectors and users of intelligence data into a National Information Sharing Environment (ISE). At these hubs, information supplied by various law enforcement agencies is brought together and made available to every other local, state and federal agency including private contractors.
You can download the Stop LAPD Spying Coalition’s ISE (Information Sharing Environment) Stalker State PDF here.
Fusion centers in the U.S. were established in response to 9/11; the ISE was authorized by the Intelligence Reform and Terrorism Prevention Act of 2004.
There are approximately 85 fusion centers in the U.S. California alone has six:
The Arizona Counter Terrorism Intelligence Center. Image source: Fusion Center Locations Revealed | Public Intelligence