Ever Heard of “Chicago Windows”? Here’s How to Spot Them.

If you’re ever in downtown Chicago strolling by an older building, look up to see the windows. And then look around at the other buildings to see theirs, too. You’ll likely notice a pattern running through them: one central window pane with a smaller one on either side. Congrats — you’ve just been introduced to the aptly named “Chicago window.”

A Chicago window has three parts, explains Rebekah Coffman, curator of religion and community history at the Chicago History Museum. There’s “a large immovable single-pane glass panel surrounded by two thinner sash windows,” she says. That means that the narrower windows on either side open, but the middle one does not. Little did I know, I’d grown up seeing this type of window at my grandparents’ South Loop condo. Once I learned what it was, I started seeing them all over the city.

When I first learned about Chicago windows, I assumed they were the same as three-paneled tripartite windows. But I was wrong! Coffman says that while the Chicago window has one immobile central panel, on the tripartite window, all the panels can open. Otherwise, the two types of windows look nearly identical.

You may think (understandably) that the Chicago window is named after the Windy City itself. But it’s actually not. The window name refers to the Chicago School of architecture, a group of collegial architects who created the window in the late 1800s.

“At the turn of the 20th century, architects such as William LeBaron Jenney, Louis Sullivan, William Holabird, and Martin Roche explored modern technology pushing spatial limits through steel-frame construction,” Coffman says. “Large structural spans allowed for expanded areas for windows. This, combined with improvements in the production of plate glass, allowed for the implementation of the three-part window and provided both increased light and natural ventilation.”

The window remains a popular architectural choice, and you can still see it in a litany of older homes and buildings, Coffman says. These buildings include the Home Insurance Building by William LeBaron Jenney (1885), the Rookery Building by Burnham and Root (1888), the Marquette Building by Holabird & Roche (1895), the Sullivan Center (built as the Schlesinger and Mayer Department Store by Louis H. Sullivan in 1899, later known as the Carson Pirie Scott Building), and the Reliance Building (started by John Root in 1890 and completed by Charles B. Atwood in 1895).

Luckily, Chicagoans typically love Chicago and are proud of its history — so new architecture often attempts to include nods to or iterations of the Chicago window, Coffman says.

“As Chicago’s early skyscraper history is under consideration as a UNESCO World Heritage site, the Chicago window is, and has been, an integral part of Chicago’s built heritage,” Coffman says. “Successful examples persist of thoughtful, sympathetic preservation and adaptation of historic skyscrapers that sensitively retain window plates, such as the Marquette Building, which underwent careful restoration in the early 2000s that included a window restoration scheme.”

If older buildings aren’t preserved, we lose the chance of maintaining that built heritage. And that goes for any city and any historic architectural element around the world.