The United States Coast Guard (USCG) is a branch of the United States Armed Forces and one of the country's seven 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 U.S. Department of Homeland Security during peacetime, and can be transferred to the U.S. Department of the Navy by the U.S. President at any time, or by the U.S. Congress during times of war. To date, this has happened twice, in 1917 and 1941, during World War I and World War II, respectively.
Created by Congress on 4 August 1790 at the request of Alexander Hamilton as the "Revenue Marine", it is the oldest continuous seagoing service of the United States. Although the U.S. Navy lists its founding as 1775 with the formation of the Continental Navy, that was disbanded in 1785, and the modern U.S. Navy in its present form was founded in 1794. As Secretary of the Treasury, Hamilton headed the Revenue Marine, whose original purpose was that of a collector of customs duties in the nation's seaports. By the 1860s the service was known as the U.S. Revenue Cutter Service and the term Revenue Marine gradually fell into disuse.
The modern Coast Guard was formed from the merger of the Revenue Cutter Service and the U.S. Life-Saving Service on 28 January 1915, as an organization under the U.S. Department of the Treasury. As one of the country's five armed services, the Coast Guard has been involved in every war from 1790 up to the Iraq War and the War in Afghanistan. As of 2012 the Coast Guard had approximately 42,000 men and women on active duty, 7,900 reservists, 32,000 auxiliarists, and 8,700 full-time civilian employees. In terms of size, the U.S. Coast Guard by itself is the world's 12th largest naval force.
The Coast Guard's legal authority differs from the other four armed services: it operates simultaneously under Title 10 of the U.S. Code and its other organic authorities, e.g. Titles 6, 14, 19, 33, 46, etc. Because of its legal authority, the Coast Guard can conduct military operations under the U.S. Department of Defense or directly for the President in accordance with Title 14 USC 1–3. The Coast Guard's enduring roles are maritime safety, security, and stewardship. To carry out those roles the Coast Guard has 11 statutory missions as defined in 6 U.S.C. § 468, which include enforcing U.S. law in the world's largest exclusive economic zone of 3.4 million square miles (8,800,000 km2). The Coast Guard motto is Semper Paratus (English: Always ready).