Construction Workers Unearthed 50-Ton Boulder at O'Hare
The 400-million-year-old rock was discovered 30 feet underground during airport construction in June 2026.
Updated on Sept. 21, 2026 in Geology
Live Poll
Do you enjoy participating in public naming contests for local infrastructure projects in your area?
Construction workers at O'Hare International Airport unearthed a 50-ton dolostone boulder in June 2026. The massive rock was found 30 feet below ground while crews were working on a stormwater detention basin for the terminal modernization project.
Why it matters
The discovery offers a glimpse into the region's ancient geological history, as the rock material itself dates back 400 million years. Officials are now engaging the public through a naming contest for the display piece currently located at the airport's Multi-Modal Facility.
The boulder weighs 50 tons and was formed 12,000 to 15,000 years ago, though the dolostone material dates back 400 million years. It was recovered from 30 feet underground during a project within the $8.8 billion terminal modernization effort.
The players
Chicago Department of Aviation
This department manages the operations and infrastructure projects at O'Hare International Airport.
Ron Pitelka
He is the excavator operator who worked alongside Matt Tracy to unearth the boulder.
Matt Tracy
He is the bulldozer operator who assisted in the discovery of the boulder during the terminal project.
The details
Excavator operator Ron Pitelka and bulldozer operator Matt Tracy discovered the boulder while moving soil between basins. The city is now managing a naming contest for the site's new permanent display, which has already received over 2,300 public proposals.
Timeline
Construction crews unearthed the boulder in June 2026.
The city continued to accept naming submissions in September 2026.
The naming contest will conclude in roughly one week.
The Big Picture
This discovery validates the Illinois State Geological Survey's bedrock mapping by providing a tangible, large-scale specimen of the area's subterranean composition. It shifts the site's profile from purely industrial to an impromptu showcase of the region's deep geological history.
The boulder has been preserved for public viewing, providing travelers and local residents an accessible opportunity to see a significant piece of Illinois' natural history. While it does not alter airport operations, it serves as a unique cultural and scientific addition to the airport's infrastructure.
The takeaway
Large-scale construction projects in dense urban areas often reveal hidden geological history that would otherwise remain buried. Residents can participate in the city's outreach by submitting names for the boulder as it transitions into a permanent display.
Further reading
Learn more about the unique terrain of the region in the Geology section.
Source note: This article includes information reported by Chicago Tribune.
Live Poll
Do you enjoy participating in public naming contests for local infrastructure projects in your area?
