The Union Trust Building, located at 501 Grant Street in downtown Pittsburgh, was erected in 1915-16 by industrialist Henry Clay Frick. The Flemish-Gothic structure's original purpose was to serve as a shopping arcade. The building is modeled after the famous Municipal Hall at Leuven, Belgium, which was partly destroyed during World War I.

Known originally as the Union Arcade, it featured 240 shops and galleries. It was a precursor to the indoor shopping malls of the present day. The steeply-pitched mansard roof is adorned with terra cotta dormers and ornaments. Atop the roof are two chapel-like mechanical towers. The decorative interior is arranged about a central rotunda, capped by a stained glass dome. The levels above the fourth floor consisted of office space.

The 11-story central light well and
stained-glass dome skylight.

Designed by Frederick J. Osterling, the building was constructed on the site of Pittsburgh's nineteenth century St. Paul's Catholic Cathedral. The Union Trust Company purchased the structure in 1923, renaming it from the Union Arcade to the Union Trust Building, as well as remodeling the first four floors.

The building's unique roof is the result of a restrictive covenant placed on the land by it's previous owner, the Diocese of Pittsburgh. The bishop at the time placed the restrictive covenant on the land when Henry Clay Frick purchased it so that, although it would now have commercial purposes, residents would always remember the cathedral once stood there.

  
The chapel-like mechanical rooms atop the steep mansard roof are reminders of St. Pauls Catholic Cathedral.

Despite the grandeur of the Union Arcade, and unlike the highly successful Jenkin's Arcade, the venture was a failure. Apparently, the stores were too far removed from the Fifth Avenue/Forbes Avenue retail core, even though it was just a block up away Kaufmann's Department Store. As a result, the upper levels of the arcade were soon converted into additional office space for the Union Trust Company, part of the growing Mellon family enterprises, leaving a small retail arcade on the first floor. The building was renamed the Union Trust Building.

In the 1980s, after the construction of the Mellon Tower was renamed Two Mellon Bank Center. After a few years the name change was reconsidered, and the building is now called the Union Trust Building/Two Mellon Center. The Union Trust Building is listed on the National Register of Historic Places.

Construction of the Union Arcade (1915-1916)

The outer facade of the Union Arcade building was completed in October 1916.