In August 1785, after the Revolutionary War drew to a close, Congress had sold Alliance, the last ship remaining in the Continental Navy due to a lack of funds to maintain the ship or support a navy. From then until 1797, the United States' only armed maritime service was the Revenue Marine, founded in 1790 at the prompting of Secretary of the Treasury Alexander Hamilton. In the same year, 1785, two American merchant ships had been captured by Algiers and then Minister to France Thomas Jefferson began to urge the need for an American naval force to protect their passage through the Mediterranean. Jefferson's recommendations were initially met with indifference. However, Congress in 1786, and the Senate in 1791, discussed various proposals for a naval force, including estimates of costs for building frigates, but none were acted upon. Only in 1793 when Algiers had captured eleven additional merchant ships was a proposal finally taken seriously.
A bill was presented to the House of Representatives on January 20, 1794, providing for the construction of four ships to carry forty-four guns each, and two ships to carry thirty-six guns each — by purchase or otherwise. The bill also provided pay and sustenance for naval officers and sailors and outlined how each ship should be manned in order to operate them. Opposition to the bill was strong and a clause was added that should peace be established with Algiers the construction of the ships was to cease.
Piracy had not been a problem when the American colonies were a part of the British Empire; the Royal Navy protected American vessels, since they belonged to subjects of the British Crown. After the American Revolutionary War, however, that protection was lost, and many foreign powers found that they could harass American merchant ships with impunity. Indeed, once the French Revolution started, Britain also started interdicting American merchant ships and there was little the fledgling American government could do about it. This was a major philosophical shift for the young Republic, many of whose leaders felt that a Navy would be too expensive to raise and maintain, too imperialistic, and would unnecessarily provoke the European powers. In the end, however, it was felt necessary to protect American interests at sea.
In March 1796, as construction of the frigates slowly progressed, a peace accord was announced between the United States and Algiers. In accordance with clause nine of the Naval Act of 1794, a clause that specifically directed that construction of the frigates be discontinued if peace was established, construction on all six ships was halted. After some debate and prompting by President Washington, Congress passed an act on 20 April 1796 allowing the construction and funding to continue only on the three ships nearest to completion: United States, Constellation and Constitution.
By late 1798 however, France began to seize American merchant vessels and the attempt at a diplomatic resolution had resulted in the XYZ Affair, prompting Congress to approve funds for completion of the remaining three frigates: President, Congress and Chesapeake.
Over the next 20 years, the Navy fought the French Navy in the Quasi-War (1798–99), Barbary states in the First and Second Barbary Wars, and the British in the War of 1812. After the War of 1812, the U.S. Navy was at peace until the Mexican–American War in 1846, and served to combat piracy in the Mediterranean and Caribbean seas, as well fighting the slave trade. In 1845, the Naval Academy was founded. In 1861, the American Civil War began and the U.S. Navy fought the small Confederate Navy with both sailing ships and ironclad ships while forming a blockade that shut down the Confederacy's civilian shipping. After the Civil war, most of the its ships were laid up in reserve, and by 1878, the Navy was just 6,000 men.The U.S. Coast Guard claims to be the oldest floating nautical service of the United States since they slowly amalgamated the various life-saving and revenue cutters and then the lighthouses and all the rest of the things they do so well on a shoestring budget.
As you can see from reading the above, once we had an actual Navy the temptation to use it proved irresistible and use it we did. The United States Marine Corps may well quibble with the notion that the USCG is the oldest nautical service since there is some quaint notion that passengers can be nautical if they want to be provided they are embarked on some sort of floating contraption. The Marines have been around since 1775.
However, it is good and proper to celebrate even the temporary establishment of a naval service at any point in the past and this calls for a Party! On the other hand, think where we'd be on the Jones Act if our gutless Congress still issued letters of Marque and Reprisal and let privateers sweep the oceans for prizes. They'd have a hasty way with mere pirates and soon that scourge would be driven from the worlds oceans and seven seas leaving plenty of opportunity for riches and advancement in America's Privateer Fleets.