The Union Trust Building was erected in 1921 on the site of the Null House, a hotel that was owned by Harrison Null and later Levi Portzer.
The site had become a fixture in the history of the town because it was a popular place to stay and located very near the courthouse.

The Union Trust Company was formed in 1921 as one of the several emerging banks in Greensburg. It erected this building after purchasing the Null House property and opened for business about a year later. The building for many years had a corner clock that became a fixture in town, along with the more visible clock at the top of the Westmoreland County Jail behind the courthouse.

After the depression began in 1929, Union Trust merged into First National Bank in 1931. First National Bank became one of two banks that survived the Depression, later known as Southwest Bank and more recently First Commonwealth Bank. Since the merger with First National in 1931, the building has been used for offices, but the clock remained in place until more modern times.

In November 2004, the Westmoreland Cultural Trust purchased the Union Trust Building from Red Oak Associates, LLP, and in September of 2005, relocated its administration office to 102 N. Main Street. 

In addition to housing the Trust’s main office, the Union Trust Building is also home to Dante Bertani, Attorney at Law; Moody, McElrath & Johnston, Attorneys at Law; Stage Right (youth acting/dance/theatre school) and Big Brothers Big Sisters of the Laurel Region.