When did the American War of 1812 actually end?

The War of 1812 had six official endings: one for at land and five for at sea. The Treaty of Ghent states: "All hostilities both by sea and land shall cease as soon as this Treaty shall have been ratified by both parties as hereinafter mentioned." The American Senate ratified the treaty on February 16th, 1815, making this the earliest defensible date for the end of the war.

Consequential fighting on land lasted right up until ratification, well past the Battle of New Orleans. Andrew Jackson and the British invasion force knew that the war hadn't ended with the Battle of New Orleans. Jackson refused to rescind his order for martial law in New Orleans until he received some indication that peace had been reached by negotiators in Europe (Brands p. 287).

The British, realizing the vulnerability of the Gulf coast, sailed away from New Orleans to American-occupied Spanish-owned Mobile Bay. The Second Battle of Fort Bowyer (February 7-12, 1815) was the last land battle between the British and Americans.* It was the beginning of a British campaign to take Mobile from the Americans. Despite Jackson's boast that "ten thousand men cannot take it," the fort surrendered to the British after a five-day siege.

With Fort Bowyer captured, the British prepared to march on Mobile itself. They postponed their attack upon receiving news of the Treaty of Ghent, and they withdrew from the area altogether when they learned that the American Senate had ratified the treaty on February 16.

How important was the Second Battle of Fort Bowyer? The Mobile area was the only territory that changed ownership due to the War of 1812. Because it was Spanish-owned, Mobile was not covered in the Treaty of Ghent. It's possible that if the British force had been able to take Mobile before news from Ghent arrived, then the Americans would not have acquired Mobile until later in their history. Mobile would became the second largest cotton-exporting port in the United States, so a long-term consequence of the acquisition of Mobile was the intensification of slave agriculture in the deep South.

Five Endings for the War at Sea: The Treaty of Ghent specified five specific dates after which prizes taken at sea would be invalidated. Ships further from the North American Coast could keep prizes up to 120 days after ratification. For details for the five ending dates for the various naval theaters, see "Article the Second":

Immediately after the ratifications of this Treaty by both parties as hereinafter mentioned, orders shall be sent to the Armies, Squadrons, Officers, Subjects, and Citizens of the two Powers to cease from all hostilities: and to prevent all causes of complaint which might arise on account of the prizes which may be taken at sea after the said Ratifications of this Treaty, it is reciprocally agreed that all vessels and effects which may be taken after the space of twelve days from the said Ratifications upon all parts of the Coast of North America from the Latitude of twenty three degrees North to the Latitude of fifty degrees North, and as far Eastward in the Atlantic Ocean as the thirty sixth degree of West Longitude from the Meridian of Greenwich, shall be restored on each side:-that the time shall be thirty days in all other parts of the Atlantic Ocean North of the Equinoctial Line or Equator:-and the same time for the British and Irish Channels, for the Gulf of Mexico, and all parts of the West Indies:-forty days for the North Seas for the Baltic, and for all parts of the Mediterranean-sixty days for the Atlantic Ocean South of the Equator as far as the Latitude of the Cape of Good Hope.- ninety days for every other part of the world South of the Equator, and one hundred and twenty days for all other parts of the world without exception.

* There were some isolated skirmishes between American forces and British-allied Native Americans after peace had been declared, but these were of less significance.