and steel beams and girders. The front and rear walls of 253 Broadway were load-bearing walls below the 6th floor and carried by girders above that story. 253 Broadway's floors are built upon steel beams infilled with flat terracotta arches and covered with cement. 253 Broadway's structural beams were laid out so that the floors could carry a total live and dead load of . All of the interior partitions were made of terracotta or fireproof blocks. The main corridors in 253 Broadway were wainscoted with marble, and mosaic floor tile was used in the halls and other areas. 256 Broadway uses a skeletal frame made almost entirely of wrought steel, with self-supporting outer walls made of marble. Terracotta and brick was used to enclose the interior steel frame. The curtain walls ranged in thickness from in the two basement levels to on the upper stories. The foundations of 256 Broadway were excavated to a depth of . There are structural columns in the center of 256 Broadway's lot as well as on the edges. 256 Broadway's structural beams were laid out so that the floors could carry a total live and dead load of . The interiors used wooden floors, and as built, the stairs and elevator screens were of cast iron, wrought iron, and marble. "Costly marbles" were used to decorate the lower floors' corridors. Interior The southern half of 253 Broadway's ground floor is a room, which housed Postal Telegraph's shipping, messenger, delivery, and warehouse operations. The 2nd through 9th floors were intended for use by other tenants; the 2nd floor had a banking space while the 3rd through 9th floors contained offices. The 10th and 11th floors were used as Postal Telegraph's main offices. The ground and 2nd floors have ceilings of , while the 3rd through 11th floors have ceilings of . The 12th floor had a ceiling of and contained Postal Telegraph's switchboards, transmitters, and receivers. Iron stairways with marble steps extended from the ground floor to the roof, and four elevators were provided: two elevators serving all floors and two others running from the lobby to the four upper floors. The elevators used call buttons, a then-new technology that the New York Tribune said eliminated the need for passengers to request elevators by yelling "up" or "down". The original elevators were themselves the first electric elevators commissioned by Frank J. Sprague. The Postal