Castle was built in 1969 in Oakdale Village and was named after Henry Anson Castle, the founder of North St. Paul. Mr. Castle once owned the property that the school is built on.
The school was built with a non-graded philosophy, which was popular at the time. Rooms were designed with walls that opened into large, common areas, providing academic flexibility. During the 1969-1970 school year, Castle was home to 350 students.