In 1976, it was designated a National Historic Landmark, and in 2006, also named a National Historic Civil Engineering Landmark by the American Society of Civil Engineers.



Photo above: Philadelphia City Hall seen from the north at Arch Street. On the left is the Masonic Temple. Author: Beyond My Ken

The  World's largest free-standing masonry building was designed by Scottish-born architect John McArthur Jr. and Thomas Ustick Walter in the Second Empire style, and was constructed from 1871 to 1901 at a cost of $24 million. City Hall's tower was completed by 1894, although the interior was not finished until 1901. Designed to be the world's tallest building, it was surpassed during construction by the Washington Monument and the Eiffel Tower. Upon completion of its tower in 1894, it became the world's tallest habitable building.

At 548 ft (167 m), including the statue of city founder William Penn atop its tower, City Hall was the tallest habitable building in the world from 1894 to 1908.

It was the tallest clock tower in the world when it was completed. The tower features a clock face on each side that is 26 ft (7.9 m) in diameter. The clock faces are larger in diameter than those on Big Ben which measure 23 ft (7 m).

In the 1950s, the city council investigated tearing down City Hall for a new building elsewhere. They found that the demolition would have bankrupted the city due to the building's masonry construction.

The World's largest free-standing masonry building houses three branches of government: the city's executive branch (the Mayor's Office), its legislature (the Philadelphia City Council), and a substantial portion of the judicial activity in the city (the Civil Division and Orphan's Court of the Pennsylvania Court of Common Pleas for the First Judicial District are housed there, as well as chambers for some criminal judges and some judges of the Philadelphia Municipal Court).

City Hall has been a filming location for several motion pictures including Rocky (1976), Blow Out (1981), Trading Places (1983), Philadelphia (1993), 12 Monkeys (1995), National Treasure (2004), Transformers: Revenge of the Fallen (2009), and Limitless (2011).

The GUINNESS WORLD RECORD for the Largest masonry dome was set by the concrete dome of the Pantheon in Rome, Italy, which measures 43 m (142 ft) across, has the greatest span of any dome constructed only of masonry (that is, unreinforced stone or brick). It rises 22 m (71 ft) above its base.

GUINNESS WORLD RECORDS also recognized the world record for the Tallest un-reinforced masonry structure; at 169.3 m (555 ft 5 in) the Washington Monument in Washington DC, USA, is the tallest stone structure in the world that is constructed entirely without any steel reinforcement.