St. Mary's is the oldest school in Calgary which was founded in 1885. The school was opened by the Faithful Companions of Jesus. The leader of the school was Mother Mary Greene. The school was built in several locations. Today, St. Mary's High school is located at 111 - 18 Avenue SW which is across the river to the Talisman Centre.
From 1957 to 1969 the current school served as a boys only school for male high school students. The female high school students attended St. Mary's in a building which is now known as Our Lady of Lourdes.
In 1970, both male and female high school students attended school in the current building. The current building has undergone two major renovations to bring the structure to current code.
St. Mary's suffered major damage during the 2013 Calgary flood which left the basement in total ruin. After a year of repairs the school opened the basement to include state of the art equipment and facility.
Today, the school operates with a population of just over 1,060 students from grades 10 to 12.