The Duquesne Brewery clock is located atop the old brewery building at Mary Street and South 21st Street. The historic clock, which towers over Pittsburgh's South Side, boasts the largest single-clock face in the United States, and the third largest in the world.

Although the world-famous Pittsburgh clock has become linked forever to the history of the Duquesne Brewing Company and it's flagship brew, Duquesne Pilsener, the origin of the eighty-seven year old timepiece is tied to another iconic drink, Coca-Cola.

  
The massive Coca-Cola billboard and it's historic 60-by-60 foot clock in March 1936.

In 1931, the Coca-Cola Company contracted with clockmaker Audichron to create large outdoor billboards which included clocks. In 1933, a massive billboard was planned for the city of Pittsburgh.

The highlight of the billboard was a 60-by-60 foot clock face, with a 35-foot minute hand and a 25-foot hour hand, both made of laminated aluminum and weighing over a ton apiece. The Coca-Cola Clock was, at the time, the world's largest single-face clock and nearly twice the diameter of London's Big Ben.

The Coca-Cola billboard and clock 1936.

After being delivered to Pittsburgh by rail, the Coca-Cola Clock was installed on the giant billboard, erected on the steep slope, below what is now McArdle Roadway, facing downtown Pittsburgh.

The billboard and clock remained on the Mount Washington hillside from 1933 until 1961. After initially marketing Coca-Cola, beginning in 1938 it was used to advertise a succession of beverages, including Fort Pitt, Ballantine, Carling, and Schlitz beers.

  
The Pittsburgh Clock was used to market Fort Pitt Beer in 1938,
and carried a Ballantine Beer advertisement in 1951.

During the 1940s and 1950s, while the giant Pittsburgh clock loomed over Carson Street, the Duquesne Brewing Company, which was founded in 1899, was flourishing as one of the area's top breweries. In 1950, the company dedicated a new brewery building on the South Side.

A decade later, in 1961, amidst a decline in sales, the now struggling company purchased the landmark Pittsburgh clock and had it installed on the tower of the brewery building. The clock face was emblazened with the slogan "Have a Duke," and remained that way for nearly three decades.

  
The clock was moved to the Duquesne Brewery building in 1961 and suggested that Pittsburgher's "Have a Duke."

The Duquesne Brewing Company ceased operation in 1972 and the brewery buildings were eventually sold. Since the sale of the brewery, the giant clock, has been used as premium advertising space for numerous corporations.

Visible from over a mile away and brightly lit in the evening, the clock face has promoted Stroh’s Beer, Iron City Beer, WTAE-TV, Equitable Gas and, most recently, the AT&T Corporation. It underwent a $44,000 renovation in 1999. Since 2017 the clock has been running without any corporate advertisement.

  
Over the years the clock has been used to advertise Stroh's Beer and Equitable Gas.

  
The landmark Pittsburgh clock is brightly lit in the evening and visible from well over a mile away.

  
The Duquesne Brewery Clock being affixed with the AT&T logo in 2009.
The workers give an idea of the grand scale of the clock hands.

Almost ninety years of age, the city's landmark timepiece continues to tick off the hours and minutes with the same precision as it did back in the days when it was known world-wide as Pittsburgh's "Coca-Cola Clock."