United States Department of Homeland Security
The United States Department of Homeland Security (DHS) is a federal agency comprised of three main organizations responsible for immigration policies, procedures, implementation and enforcement of United States laws, and more.
These DHS organizations include United States Citizenship and Immigration Services (USCIS), Customs and Border Protection (CBP) and Immigration and Customs Enforcement (ICE). Together they provide the basic governmental framework for regulating the flow of visitors, workers and immigrants to the United States.
USCIS is responsible for the approval of all immigrant and nonimmigrant petitions, the authorization of permission to work in the U.S., the issuance of extensions of stay, change or adjustment of an applicant's status while the applicant is in the U.S, and more.
CBP is responsible for admission of all travelers seeking entry into the United States, and determining the length of authorized stay, if the traveler is admitted. Once in the United States the traveler falls under the jurisdiction of DHS.