In the heyday of the DuPont Company in the 1950s, greater Wilmington became the sixth wealthiest city in the United States, which attracted Philadelphia developers to build a series of luxury apartment towers just west of downtown. This sixteen-story tower for developer Mayer I. Blum and Sons contained 182 units, all air-conditioned. Construction was delayed by the blue rock boulders encountered when sinking the seventy-six caisson pilings. Openwork concrete-block screens at the side of the projecting balconies add a rare decorative touch. The fifteen-story Dorset (1959–1960) stands nearby at 1301 Harrison Street. Designed by Wilmington architect Morton E. Bleich for Philadelphia developer Ephraim J. Frankl, the Dorset featured Vermont granite trim at the foundations and projecting concrete slabs as sunshades at each floor.