In the wake of the September 11th terrorist attacks, then-president George W. Bush created the Office of Homeland Security to deal with terror threats. The DHS was officially created on November 25th, 2002 under the Homeland Security Act. It incorporated 22 agencies into a single cabinet with the broad task of homeland security. These agencies included agencies like the Secret Service, but neither the FBI or the CIA were included following a minor controversy. The first official acts were undertaken by the DHS on January 24th, 2003.
In March of 2004, the National Incident Management System (NIMS) was formed to coordinate emergency preparedness and incident response and recovery within various levels of government. In December of that same year the National Response Plan (NRP) was created to provide a plan in the event of terrorist attack or natural disaster. On March 22nd, 2008 this plan was replaces with the National Response Framework. In October of 2009 the National Cybersecurity and Communications Integration centre was opened to coordinate government efforts to protect computer networks and infrastructure.
Currently the DHS is headquartered at the Nebraska Avenue Complex in Washington, DC. It contains 22 child agencies drawn from as widely disparate fields as Justice, Energy, Transportation and the Treasury. Currently there are about 216,000 people employed by the DHS. It is a member of the US Intelligence Community, and as such is lead by the Director of National Intelligence, who oversees all members of the IC.