The Fascinating Alignment of Cities and the Sun

In Chicago, a unique phenomenon known as “Chicagohenge” occurs when the sun aligns perfectly with city streets like Kinzie and Madison. This event happens once or twice each year, drawing attention to the city’s design. The fall equinox, as seen on September 22, 2017, highlights these alignments.

As days become shorter with the fall equinox, many cities across the U.S. offer a chance to witness this striking alignment. Streets oriented towards the cardinal directions allow the sun to rise and set directly between buildings, reminiscent of ancient observances such as those at Stonehenge.

Geoff Boeing, an urban planning expert at the University of Southern California, describes how city layouts help frame the universe. Michelle Nichols from the Adler Planetarium explains that Chicago’s skyscrapers enhance this effect, making “Chicagohenge” a breathtaking sight.

This alignment is a result of Chicago’s street design, which follows the cardinal points. Nichols suggests that all you need is a wide east-west street; a bit of elevation can also help. The 2026 fall equinox will arrive on September 22, offering equal hours of day and night in the Northern Hemisphere.

Other City Alignments

Cities like Washington, D.C., and Phoenix, with grid layouts, provide opportunities to observe similar “henge” moments. Boeing discusses how ancient cities were built with cosmic urban plans. For example, Tenochtitlan, the precursor to Mexico City, was planned using astronomical knowledge as noted in a 2021 study.

Modern cities, however, align with celestial features accidentally due to grid designs, not cosmological intentions. “Even if we didn’t do it intentionally, we’re still getting the same side effects,” says Boeing. Nichols adds that these alignments are a great reminder of the sky above.

Exploring Grid Cities

Boeing, who has analyzed city street grids, notes that Chicago and Denver are prime examples of compass-aligned grids. This alignment facilitated land sales and infrastructure planning during the 19th-century westward expansion in the U.S.

Not all cities follow the compass deeply, leading to different “henge” timings. For instance, “Manhattanhenge” and “California Henge” do not coincide with equinox dates due to geographical influences rather than compass points.

Enjoy Safely

Nichols from the Adler Planetarium warns photographers to stay safe when capturing “henge” photos. Use sidewalks instead of streets to avoid danger. Additionally, drivers should be cautious during the equinox due to potential sun glare, leading to traffic disruptions.