Southside Junior High School is one of four known Romanesque Revival buildings in St. Petersburg. All were designed in the 1920s by architect Henry Taylor. The other Romanesque Revival buildings located in St. Petersburg are St. Mary Our Lady of Grace Catholic Church (1925), St. Paul's Catholic Church (1929), and the 1927 Comfort Station # 1 (designated a landmark in 1991) located along the Pier approach. It is possible that Henry Taylor was influenced by Palm Beach architect Addison Mizner's octagonal Riverside Baptist Church, which was built in 1924-25 in Jacksonville, Florida.

Southside Junior High School's facade is a modified Romanesque Revival that has been applied to a school building. It has an octagonal tower stemming from the Greek cross shape used in early Roman churches which is capped with a red tile roof and a copper finial. The building is constructed using multicolored brick similar to St. Petersburg's other three Romanesque Revival structures. The use of deeply recessed, rounded arched windows typical in Romanesque Revival style buildings are also seen on Southside Junior High School. Some of the best arches have been preserved on the second floor interior hallway where a second story was added in 1956. The three frontal entrances/exits are adorned with stone carved panels and stone carved columns.

Southside Junior High, along with Lealman Junior High, were the last schools to be built in Pinellas County until 1950. Due to the significant drop in enrollment dropped during the Great Depression. The 1926 enrollment level would not be reached again until after World War II in 1947. Southside remained a junior high school until 1972 when it was closed for one year, only to be reopened in 1973 as Southside Alternative School. In 1974, a federal program called the Student Resource Center was housed in and coordinated with Southside Alternative School.