The department was established on November 25, 2002, by the Homeland Security Act of 2002. It was intended to consolidate U.S. executive branch organizations related to "homeland security" into a single Cabinet agency. The following 22 agencies were incorporated into the new department:[7]
* Customs Service – Treasury
* Coast Guard – Transportation
* Secret Service – Treasury
* United States Citizenship and Immigration Service (formerly Immigration and Naturalization Service) – Justice
* United States Border Patrol (formerly Immigration and Naturalization Service) – Justice
* U.S. Immigration and Customs Enforcement (formerly Immigration and Naturalization Service) – Justice
* United States Federal Protective Service (part of ICE)
* Transportation Security Administration – Transportation
* Federal Law Enforcement Training Center – Treasury
* Animal and Plant Health Inspection Service – Agriculture
* Office for Domestic Preparedness – Justice
* Federal Emergency Management Agency
* Strategic National Stockpile and the National Disaster Medical System – HHS
* Nuclear Incident Response Team – Energy
* Domestic Emergency Support Teams – Justice
* National Domestic Preparedness Office – FBI
* CBRN Countermeasures Programs – Energy
* Environmental Measurements Laboratory – Energy
* National BW Defense Analysis Center – Defense
* Plum Island Animal Disease Center – Agriculture
* Federal Computer Incident Response Center – GSA
* National Communications System – Defense
* National Infrastructure Protection Center – FBI
* Energy Security and Assurance Program – Energy
From the Wiki you just linked...