The Coast Guard Is Older than the Navy.
It began its life when President Washington established the Revenue Cutter Service to enforce U.S. tariffs in 1790, and was America's only maritime defense force until the Department of the Navy was established in 1798 (the Navy officially dates its birthday back to the establishment of the Continental Navy in 1775, but that Navy was disbanded after the Revolutionary War).
Generally, while the other four branches get prime-time TV spots that chant, "Army! Navy! Air Force! Marines!" the Coast Guard is relegated to late-night TV or the occasional pre-movie blurb. It doesn't help that the Coast Guard report to a different department than the "big four", rolled up into Homeland Security with less popular agencies like Immigration Services, while the Navy and Marines kick it in the Department of Defense.note Prior to the creation of DHS, the Coast Guard was part of the Department of Transportation, and the Department of the Treasury before that.
Coast Guard Officers Train aboard a Captured Nazi Sailing Ship. The USCGC Eagle began its life in 1936 in Nazi Germany as the SSS Horst Wessel. Christened by Adolf Hitler, the Horst Wessel was intended to serve as a training ship for the German Kriegsmarine. It served the Germans for three years, but when World War II kicked off, it was sidelined.
With the defeat of Nazi Germany in 1945, the vessel was captured by the British. It eventually fell into American hands and was sailed across the Atlantic Ocean by a team of American and German seamen. Today it's the flagship of the Coast Guard and trains USCG cadets and officers in practical seamanship skills.
This being America, despite the Coast Guard's small size compared to the other military branches, it is still larger than many nation's navies and operates more ships. The Legend-class National Security Cutters, for instance, are larger and better armed than some second and third world frigates and destroyers. Of course, the USA needs a bit more oomf to its Coast Guard, considering the USCG has to police and protect the world's largest exclusive economic zone, all 11,351,000 square kilometers of it.
Coast Guard Signalman First Class Douglas Munro volunteered to support the Navy in landing Marines during the 1942 landings at Guadalcanal. When one group of Marines came under a massive Japanese counterattack while assaulting a beachhead, Munro led the evacuation of the Marine force.
While the Marines were loading onto the evacuation boats, Munro placed his boat between them and the incoming fire to protect the Marines. Munro then moved his boat to free one that had run aground before he was shot in the head by a Japanese machine gun.
Munro posthumously received the Medal of Honor for his actions in rescuing the Marines on Guadalcanal, and his medal currently has a place of honor in the National Museum of the Marine Corps.