CAPTION: Alleg. River. Sixth St. Bridge. U.S. Eng'r. Office, Pbg, Pa. Mar. 7, 1910. 1006. Sixth Street Bridge spanning the Allegheny River, showing the grade line of the proposed new bridge. NOTES: PHOTOGRAPHER: DATE: 7 March 1910. HEADING: Pittsburgh. Bridges. Sixth. #: From the Collections of the Pennsylvania Department, The Carnegie Library of Pittsburgh.