Every year around the fall and spring equinoxes, many Chicagoans stop and stand in the middle of downtown streets for the perfect photo: the sun shining directly through the Loop’s grid, illuminating the buildings in a fierce orange.
The phenomenon is known as “Chicagohenge,” and it refers to the week leading up to the fall equinox (or the week following the spring equinox) when the sun lines up exactly with Chicago’s east-west streets during sunrise and sunset. This unique phenomenon occurs because during the equinoxes, Earth is not tilted toward or away from the sun; the sun follows a path across the celestial equator, said Michelle Nichols, director of public observing at the Adler Planetarium.
“What it boils down to, and what you can see on the days of the equinoxes ... is the full sun shining right down our east-west streets,” said Nichols, who has worked at the Adler for nearly 25 years.
The name “Chicagohenge” is a nod to Stonehenge in England, a prehistoric monument that at certain points aligns with seasonal paths traveled by the sun.
“People have realized that our east-west grid of streets is sort of reminiscent of some of the more ancient places and structures that have some sort of sky alignment properties,” Nichols said.
It’s not just Chicago that exhibits this feature; Nichols said there’s a “Manhattanhenge,” too. But it occurs on different days in New York because Manhattan’s streets aren’t aligned in the same way.
This year, the fall equinox is on Thursday, Sept. 22. To see “Chicagohenge,” you need to stand on an unobstructed east-west street around sunset or sunrise in the days leading up to it.
One of Nichols’ favorite spots is at the western end of the 606 Trail, which follows a former east-west rail line.
“You have kind of an unobstructed view of the horizon there,” she said.
If you do decide to check it out, make sure you look up at the sky instead of directly into the sun. And if you miss it, you’ll get another chance in March.
Editor’s note: This story was originally published in 2019.