The United States Department of Homeland Security (DHS) is the U.S. federal executive department responsible for public security, roughly comparable to the interior or home ministries of other countries. Its stated missions involve anti-terrorism, border security, immigration and customs, cyber security, and disaster prevention and management.It began operations in 2003, formed as a result of the Homeland Security Act of 2002, enacted in response to the September 11 attacks. With more than 240,000 employees, DHS is the third-largest Cabinet department, after the Departments of Defense and Veterans Affairs. Homeland security policy is coordinated at the White House by the Homeland Security Council. Other agencies with significant homeland security responsibilities include the Departments of Health and Human Services, Justice, and Energy.

The United States Customs Service was an agency of the U.S. federal government that collected import tariffs and performed other selected border security duties.

In March 2003, as a result of the homeland security reorganization, the U.S. Customs Service was renamed the Bureau of Customs and Border Protection, and most of its components were merged with the border elements of the Immigration and Naturalization Service, including the entire U.S. Border Patrol and former INS inspectors, together with border agriculture inspectors, to form U.S. Customs and Border Protection, a single, unified border agency for the U.S. The investigative office of U.S. Customs was split off and merged with the INS investigative office and the INS interior detention and removal office to form Immigration and Customs Enforcement, which, among other things, is responsible for interior immigration enforcement. The United States Customs Service had three major missions: collecting tariff revenue, protecting the U.S. economy from smuggling and illegal goods, and processing people and goods at ports of entry.