The Regional Enterprise Tower is a 410-foot, thirty-story skyscraper in downtown Pittsburgh, formerly called the Alcoa Building. Designed to be the headquarters of the Aluminum Company of America (ALCOA), construction began in 1951 and was completed in 1953.

The construction of the Alcoa Building was a revolutionary use of aluminum in architecture. The unique aluminum walls of the building are only 1/8 inch thick, giving the building a lightweight and economical design. The entire facade of the tower is sheathed in stamped aluminum panels. The windows, sashes and frames, heating and ventilating ducts, water piping and wiring system were all made of aluminum.

Another innovation in skyscraper construction was the aluminum windows, which rotate 360 degrees so they can be washed from the inside. The glimmering Alcoa Building was another magnificent addition to the newly-emerging skyline, and another historic achievement for the City of Pittsburgh.

Some interesting notes on the Alcoa Building regard the razing of the original Nixon Theatre and the creation of Mellon Square Plaza. From December 7, 1903 until April 29, 1950, the site of the Alcoa Building was home to the first incarnation of the downtown Nixon Theater. It was described as the "world's most perfect playhouse". The sale of the site to Alcoa in 1950 was met with protests. Actress Katharine Hepburn wrote to the city before demolition, "I'm infuriated, The new skyscraper will be just another building -- maybe fascinating, but not glamorous."

Prior to the purchase of the land, the Aluminum Company of America was considering a move to New York. In an effort to keep the headquarters based in Pittsburgh, the Mellon family offered to build a parking garage and plaza adjacent to the proposed building. The offer was accepted. The company remained in Pittsburgh, and Mellon Square Plaza was constructed in the city block between the Alcoa Building and the Mellon Bank Building.

The new Alcoa corporate headquarters on Pittsburgh's North Shore.

In 2001, Alcoa relocated their corporate headquarters to a building on Pittsburgh's North Shore. The old Alcoa Building was renamed Regional Enterprise Tower, and became home to government entities, regional nonprofits and small start-up companies.

  
The Alcoa Building under construction in 1951 (left) and the completed structure, along with Mellon Park.