The trust company was created along with Central National Bank (WL16), which moved into a separate building at 5th and Market streets in 1890. The facade of Security Trust was derived from the Penn National Bank in Philadelphia (1882–1884, later demolished), also designed by the Furness company. In Frank Furness: The Complete Works, the authors give Security Trust to Furness directly, but it is plausible that draftsman E. James Dallett played an important role in both it and Penn National, his father being head of the latter bank. Security Trust featured innovations, including fireproof steel vaults and safe-deposit boxes. It was originally just three bays along Market Street, but was expanded to six in 1908 (making it even more like Penn National), with changes to the fenestration. In 1927, Brown and Whiteside remodeled the interior and, in 1930, it became the National Bank of Delaware. Alterations were made to the facade in 1961. The building is now used for a charter school.