Your walk follows Fifth Avenue, the boulevard that was Pittsburgh's answer to Fifth Avenue in New York during the Gilded Age. When Pittsburgh was the steel capital of the world and Carnegie, Frick, Mellon, and Westinghouse were accumulating fortunes not equaled until the technology era, they spent those fortunes along this corridor. Department stores, theater palaces, banks with marble halls, and hotels where the captains of industry held their meetings lined this street.
Kaufmann's department store, opened in 1871, was for generations the defining retail institution of downtown Pittsburgh. It was at Kaufmann's in 1935 that Frank Lloyd Wright unveiled the model for Fallingwater, his masterwork commissioned by the Kaufmann family. The department store became a Macy's in 2006.
The architecture along Fifth Avenue preserves the ambition of the steel era. Look up at the upper floors of the buildings you pass: the terracotta ornament, the classical cornices, the elaborate facades are all there above the modern retail signage. Henry Clay Frick, Carnegie's business partner who hired the Pinkertons for the Homestead Strike, maintained his Pittsburgh offices in this district.
Carnegie and Frick had a falling out after Homestead that lasted decades.