Financier and militia officer Henry Pellatt commissioned Casa Loma as an imposing Toronto residence after accumulating wealth through electricity, railways, insurance, and land speculation. Architect E. J. Lennox began work in 1911 on a hill overlooking the city. Hundreds of laborers and craftspeople created a steel, concrete, stone, and brick house dressed in medieval and Scottish revival forms. Towers, battlements, a Great Hall, conservatory, library, secret passages, service corridors, and modern plumbing and electrical systems made it a technologically current Edwardian mansion rather than an actual medieval castle.

Pellatt and his wife Mary moved into the incomplete house in 1914. The estate expressed social ambition, collecting, entertaining, and the unequal domestic labor supporting elite life. Plans for a large indoor swimming pool were never finished, and wartime conditions interrupted construction. Rising taxes, business reverses, and the loss of Pellatt's hydroelectric interests damaged his finances. The family left in 1924, only about a decade after occupation began. Contents were auctioned, severing many furnishings from the rooms for which they had been selected and leaving later interpreters to rebuild an impression of the household.

The building briefly operated as a hotel and entertainment venue before the City of Toronto acquired it for unpaid taxes in the 1930s. Demolition was considered, but the Kiwanis Club leased and opened Casa Loma as a tourist attraction in 1937. During the Second World War, a concealed industrial operation in the former stables helped research and assemble ASDIC submarine-detection equipment while public entertainment continued nearby. After decades of charitable operation, the city selected a private hospitality company to manage the property, adding restaurants, events, exhibitions, and seasonal installations.

Casa Loma preserves the original masonry shell, towers, stables, tunnels, many windows, woodwork, decorated rooms, and unfinished spaces, but its current interiors are a mixture of surviving fabric, restoration, replacement furnishings, themed display, and adaptive reuse. Furniture presented in a room may be period-appropriate without belonging to the Pellatts. Mechanical, electrical, fire, accessibility, catering, and event systems are modern. Exterior stone, roofs, windows, gardens, and finishes have required substantial repair. Film production and spectacle introduce temporary layers that should not be mistaken for historic decoration.

The City of Toronto owns the designated heritage property, with day-to-day operation under a commercial lease and public oversight. Admission, rooms, gardens, events, and filming can affect access. Interpretation should connect Pellatt's personal rise and fall with electricity monopolies, urban growth, domestic service, militarism, wartime research, and the long reinvention of the building as entertainment. Casa Loma is an authentic early twentieth-century mansion modeled on an imagined past, not a transplanted European fortress. Its preservation depends on clearly separating original architecture from recreated interiors and contemporary attractions.