The Illinois State Capitol, located in Springfield, Illinois, is the building that houses the executive and legislative branches of the government of the U.S. state of Illinois. The current structure is the sixth to serve as capitol since Illinois became a part of the United States in 1818. The capitol is in the architectural style of the French Renaissance and was designed by Cochrane and Garnsey, an architecture and design firm based in Chicago. Ground was first broken for the new capitol on March 11, 1869, and it was completed twenty years later for a total cost of $4,500,000. The dome is covered in zinc to provide a silvery facade which does not weather. The interior of the dome features a plaster frieze painted to resemble bronze, which illustrates scenes from Illinois history, and stained glass windows (including a stained glass replica of the state seal in the oculus of the dome). The seal featured in the top of the dome is the seal used by Illinois prior to the American Civil War. It differs from the modern seal in that the phrase "State Sovereignty" is above the phrase "National Union." After the Civil War, the legislature voted to reverse these phrases as they professed that National Union was the more important of these two concepts.