In a manner similar to the famous “Manhattanhenge” in the Manhattan area of New York City, Chicago also has its own phenomenon known as “Chicagohenge”, which occurs twice a year and never fails to captivate local residents and visitors alike.
Just like Manhattan, the streets of Chicago are laid out in a grid pattern. During specific times of the year, the sunlight at sunrise or sunset aligns perfectly with Chicago’s straight streets and tall buildings, creating a stunning golden spectacle reminiscent of a megalithic stone circle – the so-called “Chicagohenge”.
Unlike “Manhattanhenge” which occurs around the summer and winter solstices, “Chicagohenge” takes place around the days of the autumnal and vernal equinoxes. This year, “Chicagohenge” appeared from March 20 to 23 and September 19 to 22, with March 20 marking the vernal equinox and September 23 the autumnal equinox.
The Adler Planetarium points out that the equinoxes mark two times in the year when sunlight is evenly distributed, resulting in equal lengths of day and night for people to experience.
To truly appreciate the phenomenon of “Chicagohenge”, one must understand the two main factors that create this spectacle – Chicago’s grid-like street layout and the point of equinox (vernal or autumnal).
Chicago’s present grid layout can be attributed to the Public Land Survey System established in 1785, a method used for land division for sale and settlement. This urban design style has existed since the dawn of civilization, with traces found in ancient Roman and Greek sites.
The benefits of a grid pattern street layout are many, including ease of navigation, walkability, and adaptability. Additionally, it can lead to awe-inspiring astronomical and architectural events, just like “Chicagohenge”.
The name “Chicagohenge” pays homage to the famous prehistoric site – Stonehenge in England.
Previous reports by Da Ji Yuan indicate that studies suggest Stonehenge may have served as an ancient solar calendar, reflecting changes in the sun, moon, and seasons throughout the year.
For example, the stone gates along the central axis of Stonehenge align intricately with the position of the sun on the vernal and autumnal equinox days, where the sunrise and sunset align perfectly with these gates.
Regarding the equinoxes marking the point of equal day and night, the planetarium explains that as the Earth orbits the sun, it also rotates along its inclined axis. This tilt causes sunlight distribution to be uneven, leading to the changing of seasons.
During the vernal and autumnal equinoxes, the sun rises and sets due east and due west, and both the northern and southern hemispheres experience equal lengths of day and night. The vernal equinox signals the start of spring while the autumnal equinox marks the end of summer.
Due to Chicago’s perfectly laid out grid streets, when the equinoxes approach, the sun rising and setting in the east and west aligns directly with the east-west streets of Chicago, creating the phenomenon of “Chicagohenge” – where sunlight penetrates the streets between skyscrapers, bathing the east-west streets of Chicago in hues of red and orange during sunrise or sunset.
To witness “Chicagohenge”, simply find an east-west oriented street in Chicago and choose a spot 5 to 10 minutes before sunrise or sunset to admire the beauty. Popular viewing locations include the intersection of Kinzie Street and Madison Street.
September 22 marks the last day this year to gaze upon “Chicagohenge”, but due to cloud cover, the full spectacle may be obscured. The next chance to witness it will have to wait until next year’s vernal equinox.