Headquartered in Milwaukee, Wisconsin, Coast Guard Sector Lake Michigan is responsible for all Coast Guard missions on Lake Michigan and surrounding navigable waterways, including Search and Rescue, Law Enforcement, Aids to Navigation, Marine Safety, and Homeland Security. Part of the USCG's 9th District, Sector Lake Michigan is the largest of 35 Coast Guard Sectors in number of field units (22), and the 4th largest in number of personnel.