The United Stated modern Navy branch traces back to the Continental Navy established during the Revolutionary War even though it was disbanded shortly after the war. It wasn't until the Barbary Wars that Congress created the Naval Act of 1794. Though the US Navy was a key player in many wars of historical note, it wasn't really until the Civil War that it proved itself worthy of the Naval Act by effectively cutting the Confederacy ability to import needed supplies and thus ultimately winning the war.
When the Civil War came to an end it also closed a chapter in Naval history as the Navy was seen as unneeded and neglected. Until 1907 when Theodore Roosevelt ordered a demonstration of global naval capabilities was the Navy again on the forefront. Again falling to neglect, the Navy saw little action in World War I.
This all changed in December 1941 when Japanese forces attacked the naval base in Pearl Harbor starting World War II. In the following years of World War II, the US Navy again proved they had the stuff their forefathers were made of by wading into battles that still hold the public's eye today; Battle of Coral Sea, Battle of Midway, Battle of the Philippine Sea, the Battle of Okinawa, and the Battle of Leyte Gulf. When World War II was officially ended, the U.S. Naval forces and technology had grown considerably by hundreds of ships, aircraft carriers, and battleships.
This increase in forces and technology continues today and is the reason the Navy is the well oiled machine it's become. From Vietnam, Cuba, Gulf War, Afghanistan, and Iraq, the Navy's change in forward deployment methods has been honed and developed to a fine finish. Marine Corp and Coast Guard are closely linked with the Navy which is evident by their respective seals. Marines are transported and deployed by naval vessels while the Coast Guard is the "homeland Navy" in respect of Posse Comitatus which prohibits the US Navy from enforcing US laws.
To all the men and women who've chosen to serve in this distinquished branch, thank you for your sacrifice. For those who lost their lives as a result of that service, they will never be forgotten. Everytime another soldier boots up, they're thinking of those who've gone before. Everytime a civilian sees the flag wave, the memory of those lost is there. Thank you.