The British established a trading post in the area in 1722 and fortified it with a log palisade later called Fort Oswego, named after the native Iroquois place name “os-we-go” meaning “pouring out place”. The first fortification on the site of the current Fort Ontario was built by the British in 1755 and called the “Fort of the Six Nations”.
Fort Ontario was destroyed by the French upon capturing it in the Battle of Fort Ontario, during the French and Indian War. Construction of a second British fort began on the same site in 1759, but Fort Ontario was only used as a cannon emplacement. During the American Revolution, the British abandoned the Fort, and in 1778, American troops destroyed it. In 1782, the British reoccupied Fort Ontario, and didn’t forfeit it to the U.S. until 1796, thirteen years after the cessation of hostilities in the Revolution. During the War of 1812, a weaker American garrison at Fort Ontario was overwhelmed by superior British forces in order to stem the flow of supplies from the interior of New York state, but were later defeated near Oswego later that month. Throughout the 19th Century, the U.S. military maintained a presence at Fort Ontario.
During WWII the Fort was used to house interned persons, mainly Jewish refugees (see the next section, “Safe Haven”). In 1946, the Fort was transferred to the state of New York. At that time, it was used to house veterans and their families during the post-war period. Development of the fort as a historic site began in 1949, which included the “Safe Haven Museum” (see above). The current fort was built between 1839 and 1844. Major masonry improvements to the forts outer wall were undertaken, but left incomplete when in 1872, Congress canceled its funding. By 1901, the old fort was abandoned. Today, Fort Ontario is being restored to its 1867–1872 appearance. Costumed interpreters recreate the lives of the officers, men, and civilians who garrisoned the fort in 1868–1869.