The United States Coast Guard (USCG) is a branch of the United States Armed Forces and one of the seven U.S. uniformed services. The Coast Guard is a maritime, military, multi-mission service unique among the U.S. military branches for having a maritime law enforcement mission (with jurisdiction in both domestic and international waters) and a federal regulatory agency mission as part of its mission set. It operates under the Department of Homeland Security during peacetime, and can be transferred to the Department of the Navy by the President at any time, or by Congress during time of war.

Founded by Alexander Hamilton as the Revenue Marine first, and later as the Revenue Cutter Service on 4 August 1790, it is the United States' oldest continuous seagoing service. Treasury Secretary Alexander Hamilton headed the USRCS, and the branch was involved in every war from 1790 to World War I. As of August 2009^[update] the Coast Guard had approximately 42,000 men and women on active duty, 7,500 reservists, 30,000 auxiliarists, and 7,700 full-time civilian employees.