The Illinois State Capitol, located in Springfield, Illinois, houses the legislative and executive branches of the government of the U.S. state of Illinois. The current building is the sixth to serve as the capitol building since Illinois was admitted to the United States in 1818. Built in the architectural styles of the French Renaissance and Italianate, it was designed by Cochrane and Garnsey, an architecture and design firm based in Chicago. Ground was broken for the new capitol on March 11, 1868, and the building was completed twenty years later for a total cost of $4.5 million.

The Illinois General Assembly is the legislature of the U.S. state of Illinois. It has two chambers, the Illinois House of Representatives and the Illinois Senate. The General Assembly was created by the first state constitution adopted in 1818. As of 2023, the current General Assembly is the 103rd; the term of an assembly lasts two years.