Is Fort George National Historic Site haunted?
Canada Reported haunting level 3 of 5

What actually happened
In May 1813 American artillery and a landing force destroyed and captured the fort; the occupiers withdrew in December 1813 and burned the town.
The history
The British built Fort George between 1796 and 1803 as headquarters of the Centre Division on the Niagara frontier. Designated in 1921, it was later reconstructed around the surviving 1796 powder magazine.
What people report
Visitors on evening lantern tours have reported a girl's reflection in a mirror and a soldier in the tunnel beneath the ramparts.
That paragraph is reported tradition, not a claim about what is there. The history above it is sourced; the stories are recorded because people tell them.
Visiting
51 Queens Parade, Niagara-on-the-Lake, ON L0S 1J0, Canada