Louisburg, a ruined town of the province of Nova Scotia, Canada, on the S. E. side of the island of Cape Breton, in lat. 45° 54' N., lon. 59° 52' W. Its present population consists of only a few fishermen. After the surrender of the French settlements in Nova Scotia to England by the peace of Utrecht in 1713, emigrants from those settlements occupied the coasts of the neighboring island of Cape Breton, and Louisburg, so named in honor of Louis XIV., began to be fortified by the French government on a gigantic scale, with the intention of making it the strongest fortress in America, and a commanding naval, fishing, and commercial station. The town was about 2 1/2 m. in circumference, and stood upon a neck on the S. side of the harbor, a beautiful and extensive land-locked basin with an entrance half a mile broad. It was fortified by a wall from 30 to 36 ft, high, with a ditch 80 ft. broad. The main works mounted 65 heavy cannon and 16 mortars. On Goat island, at the entrance to the harbor, was a battery of 30 guns, and at the bottom of the harbor opposite the entrance was another called the royal battery, which mounted also 30 guns.

These fortifications had been 30 years in building, and had cost $5,000,000. The neighborhood of Louisburg caused great uneasiness in New England, whose fisheries were threatened with ruin by the privateers who found refuge in its harbor. In 1745, Great Britain being at war with France, Gov. Shirley of Massachusetts devised a plan for taking Louisburg, which was adopted by the legislature of that province in secret session by a majority of one vote. Forces were promptly raised, and William Pepperell was appointed commander. Connecticut sent 516 men, New Hampshire 304, and Massachusetts 3,250. Embarked in 100 New England vessels, and supported by a British squadron under Commodore Warren, they landed near Louisburg on April 30. The place was defended by a garrison of 1,600 men commanded by Ducham-bon. A detachment stationed in the royal battery on the shore of the harbor, struck with panic at the approach of the New Hampshire troops led by William Vaughan, spiked their guns and abandoned their post in the night. Vaughan took possession of it next morning, and beat off the French who attempted to recover it. Major Seth Pomroy, a gunsmith from Northampton, with 20 other smiths, succeeded in drilling out the cannon, and fire was soon opened on the city.

The siege, though prosecuted with energy and vigilance, was conducted in the most irregular and unscientific manner. On May 18 a large French ship of war laden with military stores for the supply of the garrison, and with a body of troops on board, was intercepted and taken by the English fleet. Disheartened by this disaster, and alarmed by the erection of a battery on the lighthouse cliff which commanded Goat island, the French commandant capitulated on June 17, the 49th day of the siege. This achievement called forth great rejoicings in New England and in New York and Philadelphia, and its influence was felt 30 years later at the beginning of the revolutionary war. Col. Gridley, who planned Pepperell's batteries, laid out the American intrenchments at Bunker Hill; the same old drums that beat on the triumphal entrance of the New Englanders into Louisburg, June 17, 1745, beat at Bunker Hill, June 17, 1775; and when Gen. Gage was erecting breastworks on Boston neck, "the provincial troops sneeringly remarked that his mud walls were nothing compared with the stone walls of old Louisburg." In England the news was received with bonfires and illuminations in London and other cities; and such was the impression made by the exploit, that it was considered an equivalent for all the successes of the French upon the continent, and the first lord of the admiralty declared that " if France were master of Portsmouth he would hang the man who should give Cape Breton in exchange." Nevertheless, by the peace of Aix-la-Chapelle in 1748, Louisburg was restored to France. In 1757, during the seven years' war, the earl of Loudon, British commander-in-chief in North America, collected at Halifax a force of 6,000 regulars, 4,000 provincial troops from New England, and large numbers from New York and New Jersey, with which to make an immediate attack on the fortress; but on learning that the garrison consisted of 6,000 regular soldiers, and that 17 French line-of-battle ships were moored in the harbor, he abandoned the project.

A second expedition under Gen. Amherst, consisting of 14,000 men and a fleet of 20 ships of the line and 18 frigates, sailed from Halifax, May 28,1758, against Louisburg, which was defended by the chevalier de Drucourt with 3,100 men. The harbor being secured against attack by a fleet of eight ships, and the entrance blocked by three sunken frigates, a landing was effected at the creek of Cormoran, June 8, and Gen. Wolfe, who afterward took Quebec, advanced with 2,000 men against a detached post, which was abandoned at his approach. Strong batteries were erected here, and also on the opposite side of the town, and a heavy cannonade directed against the town and the shipping in the harbor. Three of the large men-of-war were at length set on fire by bombs, and two others captured by boats. Breaches were made in the walls, and after a gallant defence the garrison surrendered, July 26, and, together with sailors and marines, amounting collectively to 5,637 men, were carried prisoners to England. The town was almost a heap of ruins.

The inhabitants were transported to France in English ships, and the fortifications were demolished.