The building was built from 1732 to 1753 as the Pennsylvania State House. Edmund Woolley and Andrew Hamilton designed it.
The Declaration of Independence was adopted here on July 4, 1776. The U.S. Constitution was drafted here at the Constitutional Convention from May 25 to September 17, 1787, in the Assembly Room.
The original wooden steeple rotted and was removed in 1781. A new, more elaborate steeple by William Strickland was added in 1828. The site became a UNESCO World Heritage Site in 1979.

