Please answer the following question: Old Catonsville High School - Old Catonsville High School also known as St. Mark's School is a historic school building located at Catonsville Baltimore County Maryland. It is a masonry schoolhouse which consists of a one-story single bay structure (built in 1878) and a three-story four bay addition (built in 1898). In 1885 the school was designated a high school and in 1910 the property was sold to the Catholic Church.It was listed on the National Register of Historic Places in 1987. Given a choice of categories company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work, the text refers to which one?
A:
Building