The fall equinox, occurring on Sept. 22 in the U.S., brings not only shorter days and seasonal change but also a striking celestial phenomenon in many American cities. When the sun rises and sets along streets running due east and west, it creates dramatic solar alignments that mirror ancient astronomical observations found at sites like Stonehenge.
Cities with grid-based street layouts aligned to compass points experience these effects most prominently. Chicago’s “Chicagohenge” phenomenon exemplifies this, where tall downtown buildings frame the rising and setting sun as it aligns with streets such as Kinzie and Madison. Other grid-planned cities including Washington, D.C., Phoenix, and Denver also offer viewing opportunities. According to urban planning experts, these alignments result from 19th-century urban planning approaches that spread across the Midwest and Great Plains during westward expansion, when orthogonal grids were adopted primarily for practical reasons—making land transactions and infrastructure development like railroads easier to manage.
Historically, humans have intentionally designed cities to correspond with celestial events and cardinal directions. Ancient examples include Tenochtitlan, the Aztec precursor to Mexico City, which was carefully planned with astronomical knowledge. In modern cities, while such alignments are typically byproducts of practical grid layouts rather than intentional cosmic design, the effect remains meaningful. Urban planners note that these recurring moments help people reconnect with the sky and broader universe, even if unintentional.
Some cities, including San Francisco and Manhattan, follow geographic rather than compass-aligned grids, resulting in different solar alignment patterns that do not occur on equinox dates. The phenomena has gained significant popularity through social media platforms, particularly during recent years when people sought shared experiences while remaining physically separated. However, officials caution that viewers should prioritize safety, avoiding street crossings for photographs and remaining aware of increased traffic and dangerous glare on east-west streets during equinox periods.
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