Illinois Capitol North Wing Rebuild Puts a Skylight Over the Senate

Illinois stripped the north wing of its Capitol down to the 1868 stonework, and what the crews found under a century of remodels is now driving the design. The Senate chamber gets an 18-foot-square stained glass ceiling with a skylight above it: 105 panels, 6,566 pieces of glass, and a sight line from the floor up toward the dome that senators have not had in living memory.

Project Scope

Core Construction Services of Illinois holds the construction contract at $243.5 million. Vinci Hamp Architects of Chicago leads the restoration with Phil Hamp as principal, and Henneman Engineering handles mechanical, electrical and plumbing. The scope covers the full north wing including the Senate chamber, a new underground visitor entrance at street level with queuing and security screening, renovated basement orientation space, and a new underground parking structure. Counting the garage, the program is now reported around $350 million. The wing has been closed to the public since spring 2025.

Why It Matters

The procurement is worth studying on its own. The state estimated $170 million and received exactly one bid, at $243.5 million, or $73.5 million over. That is what historic restoration risk costs when a bidder has to price unknown conditions behind plaster in a 158-year-old building that has to stay standing, and it is a data point every public owner planning a landmark rehab should have in front of them. The gap was not padding. Demolition confirmed it, turning up historic fabric and structural conditions that 20th-century remodels had buried.

The Illinois Capitol’s dome stands higher than the U.S. Capitol’s, and it is the tallest non-skyscraper statehouse in the country. Reopening it with a restored chamber and a visitor entrance that does not route the public through a service door is the point. Crews are working toward an opening before winter.

Project Team & Details