Opened in 1985 as the State of Illinois Center, the building was renamed in 1993 to honor former Illinois Governor James R. Thompson. The JRTC is a 17-story marble, granite, glass, and steel structure, encompassing approximately 1.2 million sq. ft. of enclosed area and seated on nearly 3-acre site. The building’s envelope slopes in height to create a southeast facing exposure, topped by a cylindrical skylight, 75 feet above the roof level. The sky-lit rotunda is 160 feet in diameter and is surrounded by 16 floors of office space, which is open to the atrium below.