What is the Department of Homeland Security?

The Department of Homeland Security is the federal department responsible for protecting the United States from terrorist attacks, securing borders, enforcing immigration laws, responding to disasters, and addressing other threats to national security at home. Created by Congress in 2002 in response to the September 11, 2001 terrorist attacks, it was the largest reorganization of the federal government since the creation of the Department of Defense in 1947. The Homeland Security Act of 2002 combined 22 existing federal agencies into a single new department.

Tom Ridge, who had served as the first head of the White House Office of Homeland Security after September 11, became the first Secretary of Homeland Security. The department's headquarters is at the St. Elizabeths West Campus in Washington, D.C. With more than 240,000 employees, the Department of Homeland Security is the third-largest federal department after Defense and Veterans Affairs.

It operates a wide range of agencies. U.S. Customs and Border Protection enforces immigration and customs laws at U.S. borders and ports of entry, including the Border Patrol, which patrols areas between official border crossings. U.S. Immigration and Customs Enforcement (ICE) handles immigration enforcement within the country, including arrests, detention, and deportations of people who entered without authorization or violated visa terms. U.S. Citizenship and Immigration Services (USCIS) processes applications for visas, green cards, naturalization, and other immigration benefits. USCIS administers the citizenship test that this study guide prepares applicants to pass.

The Transportation Security Administration screens passengers and baggage at U.S. airports. The U.S. Coast Guard, which operates under DHS in peacetime and the Department of the Navy in wartime, performs maritime law enforcement, search and rescue, and fisheries enforcement. The Federal Emergency Management Agency (FEMA) coordinates federal disaster response and recovery. The U.S. Secret Service protects the President, Vice President, foreign dignitaries, and investigates financial crimes. The Cybersecurity and Infrastructure Security Agency works to defend federal networks and critical infrastructure from cyberattacks.

The Secretary of Homeland Security leads the federal response to terrorism, immigration policy, and natural disasters. Recent Secretaries include Kirstjen Nielsen, Alejandro Mayorkas, and Kristi Noem.