The United States Coast Guard (USCG) was born on August 4th, 1790 as what was then known as the "Revenue Marine" and, later, the "Revenue Cutter Service". Its duties have always involved policing American waters in an effort to curtail various smuggling operations into and out of the United States as well as enforcing maritime laws while protecting vital regions. At the time of its inception, the USCG stood as the only armed surface fleet in service with America (the Navy Department was not formed until 1798). It was not until 1915 that the Revenue Cutter Service and the Life-Saving Service were melded together to become the "United States Coast Guard" that we know today.
The USCG operates under the banner of the Department of Homeland Security in times of peace. During wartime, by order of the President, the USCG falls under management of the United States Navy (USN) and, as such, has ranks (or "rates") that follow very much in line with those as offered by the USN (with the exception of the "Seaman" recruit rank and some insignia colors).
Women first made their mark in the USCG in the 1830s and USCG members were active participants (and award recipients) during the famous D-Day landings at Normandy, France on June 6th, 1944. Today, the USCG operates small- and medium-class surface ships, rescue helicopters, fixed-wing surveillance aircraft and several UAVs.