Most of these agencies were located in the Directorate of Border and Transportation Security (BTS), which was charged with securing the borders; territorial waters; terminals; waterways; and air, land, and sea transportation systems of the United States; and managing the nation's ports of entry. The U.S. Customs and Border Protection (CBP)

CBP combined portions of the previous border law enforcement agencies under one administrative umbrella. As currently comprised, the USBP is the uniformed law enforcement arm of the Department of Homeland Security. At official ports of entry, CBP officers are responsible for conducting immigrations, customs, and agricultural inspections on entering aliens. Unlike CBP, whose jurisdiction is confined to law enforcement activities along the border, ICE special agents investigate immigrations and customs violations in the interior of the United States. Conclusion

This report has briefly outlined the roles and responsibilities of the four main agencies within the DHS charged with securing our nation's borders: the CBP, ICE, the U.S. Coast Guard, and the TSA.
After the massive reorganization of federal agencies precipitated by the creation of the Department of Homeland Security (DHS), there are now four main federal agencies charged with securing the United States' borders: the U.S. Customs and Border Protection (CBP), which patrols the border and conducts immigrations, customs, and agricultural inspections at ports of entry; the U.S. Immigrations and Customs Enforcement (ICE), which investigates immigrations and customs violations in the interior of the country; the United States Coast Guard, which provides maritime and port security; and the Transportation Security Administration (TSA), which is responsible for securing the nation's land, rail, and air transportation networks. This report is meant to serve as a primer on the key federal agencies charged with border security; as such it will briefly describe each agency's role in securing our nation's borders. This report will be updated as needed.