The High School, as it was originally called, opened in the spring of 1893. It was renamed Central High School in 1924 when other high schools were opened. The school reflected the flamboyant attitude of the boom years. Built at a cost $104,460, the building had many modern conveniences not seen in other buildings of its time including thermostatically controlled heating and electric bells.
The first year's enrollment was 290 students and nine teachers. But with the large growth in the city those numbers swelled to 965 by 1913. The school was now too small and a new addition was planned. The proposed addition was to be built of red brick and of a different style. The city's womens' clubs forced a special election where voters agreed to spend more money to have the same stone material and architectural style. The addition cost $225,000.
The original building was built of No. 1 prentiss sandstone. When the addition was added, the new sandstone was of a different color. The decision was made to "smoke" the outside of the building to match the original stone.
Enrollment continued to grow and in 1930 the interior of the building was completely remodeled and a fourth floor was built over the original building. The hip and angled roof line was replaced with flat roofs.
The school was closed in 1972 with the construction of three new schools to take its place. The Castle on the Hill Association (COHA) was formed to find a new use for the building by restoring and renovating it. The school was listed on the National Register of Historic Places in 1973 and appeared frequently on the Iowa Historic Preservation Alliance's annual ranking of the state's most endangered historic buildings. On July 1, 1976, COHA purchased the building from the Sioux City Community School District for $1. The non-profit organization operates the Castle Gift Shop as a fund-raiser. The "Dungeon" gymnasium has been renamed "Julie Goodson Hall" and other portions of the building are used by other non-profit organizations. In 2000, COHA contacted NuStyle Development Corp. which had a track record of conversion projects including the Old Market Lofts, the Bull Durham Apartments, the Farnam Building and Immaculate Conception School, all in Omaha. After extensive renovations, the Castle on the Hill Apartments had its grand opening in 2003.