Library and Archives Canada
Carleton Island is located in U.S. waters near the middle of the south channel of the St. Lawrence River. It sits seven miles from Lake Ontario and about three miles from the village of Cape Vincent, NY. The island contains 1,274 acres of land      

Today, Carleton Island has no great political importance to either the United States or Canada. The situation was very different in the late 18th century. Both modern countries were originally colonies of Britain, but the Thirteen Colonies declared their independence in 1776.

Carleton Island occupied a strategic point between the revolting colonies and the loyal British Colony of Canada. It was called Deer Island when first used by British merchants in the 1770s. The large vessels which sailed on Lake Ontario were poorly suited to navigating the St. Lawrence River. Goods were brought up from Montreal in small boats to the island and then transferred to the larger lake vessels. 

 In 1777, a British army under General Barry St. Leger used Deer Island as a staging area for the western part of the Burgoyne Campaign. After their defeat at Fort Stanwix, Deer Island was again used in their retreat. The Burgoyne campaign defeat in the Battle of Saratoga was the first major British defeat of the American Revolution.  The British lost not only an entire field army, but access to the Mohawk Valley, which they’d used to supply their western posts at Niagara, Detroit, and other strategic locations. 

To find a new supply route, the British looked to the St. Lawrence River. In August, 1778, Governor General of Canada, Frederick Haldimand, instructed Lt. William Twiss of the Royal Corps of Engineers to select a site at the Eastern end of Lake Ontario to play a role in the new supply route. John Schank of the British Royal Navy assisted Twiss.

 After reviewing both the abandoned French fort at Cataraqui and Deer Island, Twiss and Schank selected Deer Island. Twiss renamed the island Carleton after Major General Sir Guy Carleton, the governor of Quebec. Twiss outlined the design of the docks, shipways, hospital, fortifications and barracks.  After designing the major earthworks known as Fort Haldimand, Twiss returned to Montreal, leaving men from the Royal Corps of Engineers to oversee the construction. 

 The British base at Carleton Island would continue to be important through the rest of the revolution. It served as one of the major staging areas for military actions against the Mohawk Valley. Its most important function was transshipment of supplies to the western posts. It also acted as the headquarters for navel operations on Lake Ontario and the Upper St. Lawrence River. The shipyard built two major vessels as well as several gunboats and maintained the Lake Ontario fleet. 

 By 1782 the entire west end of the island was occupied. Records indicate at times over a thousand merchants, camp followers, soldiers, sailors, Indians and displaced loyalists lived on the island.  When the Treaty of Paris ended the American Revolution in 1783, the British army abandoned new activities on Carleton Island. Though major hostilities were over, a new need arose to resettle loyalist families who were displaced from the Mohawk Valley. To this end, the British reoccupied both the post at Oswego and the old French post at Cataraqui and renamed it Kingston. 

British occupation of Carleton Island continued to decline. In 1785, transshipment for government stores was relocated from the island to Kingston.  In 1888 the naval yard was also relocated.  Technically the island was ceded to the U.S. by the Jay Treaty in 1796 yet in reality Britain still held Carleton Island at the outbreak of the War of 1812. The base, once one of the most vital sites in the province of Canada (1778 to 1783), was eventually ceded to the U.S. as the only land change resulting from the War of 1812.  

 For the first half of the nineteenth century the bays at the head of the island played a role in the lumber trade. In 1898 a grand Villa was constructed at the islands head during the Golden Age of the Thousand Islands. Most of the island was used primarily for cattle grazing until land development in the 1980s.  

1) For more information on  Frederick Haldimand, Lt. William Twiss, John Schank and Sir Guy Carleton, see the Dictionary of Canadian Biography