CAPTION: 643. Sixth Street Bridge and Skyline, Pittsburgh, Pa. 6A-H139. NOTES: Reverse: Pittsburgh is a city of bridges and the 6th Street Bridge is one of many bridges spanning the Allegheny River. Minsky Bros. & Co., Publishing Division, Pittsburgh, Pa. PHOTOGRAPHER: DATE: HEADING: Pittsburgh. Bridges. Sixth. #: From the Collections of the Pennsylvania Department, The Carnegie Library of Pittsburgh.