The predecessor of this school opened in 1892 as the Junction High School. It was then located in a wooden church, formerly the Victoria Presbyterian Church and now the site of St. Cecilia´s Catholic Church. Increasing population in the area called for a permanent building. Land for the school was purchased for $7000.

1894: The oldest part of the current structure first opened. At this point, the building consisted of 5 classrooms, staff room, library, science room, assembly hall, and a room later used for commercial work. The 3-storey Romanesque-style school in red-brick was designed by John Ellis. It featured a tower, arches, and basket-weave red brickwork. Before development grew around the building, it was surrounded by open land and sometimes referred to as "The Castle on the hill."

1903: School became a Collegiate Institute.

1909: School named changed to Humberside Collegiate Institute after the annexation of the City of West Toronto to Toronto.

1911: Extension to the west-side of the building to add 7 classrooms, 2 science rooms, and a gymnasium in the basement. This addition, following the Romanesque style of the original building, was designed by C.H. Bishop.

1923-25: 3-storey addition with 6 classrooms added to north end of building.

1924: 900-seat, 2-storey auditorium and girls' gymnasium built.

1925: 6 classrooms added to north end of building.

1931: South extension in the Victorian Gothic style added 11 classrooms, a boys' gymnasium, swimming pool, 3 science rooms, 4 committee rooms, and a cafeteria. Brick was arranged in a diamond-pattern, Corinthian capped columns, Gothic windows. Addition/renovation by C.E. Cyril Dyson and his assistant Arthur James Freestone (possibly started 1927).

1966-67: Construction began on a wing, adding several classrooms and labs, in the north parking lot. The auditorium was converted into a library. Both projects completed in 1967. Most of the 1894 building demolished and replaced with a new auditorium, cafeteria, and music rooms. The existing building undergoes extensive renovations and conversions.

• Architect - William England  <-- More buildings by this architect.
• Architect - C.E. Cyril Dyson  <-- More buildings by this architect.
• Architect - James Augustus Ellis  <-- More buildings by this architect.
• Architect - Arthur James Freestone  <-- More buildings by this architect.
• Architect - C.H. Bishop  <-- More buildings by this architect.