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Illinois Fossil Day: Ancient Giants Found Beneath Chicago Suburbs
Chicago, IL – Happy National Fossil Day! Long before Chicago's skyscrapers, suburban neighborhoods and busy expressways, Illinois was home to enormous Ice Age mammals, tropical forests and creatures s
By Audrey Sloan · 2026-10-15T13:27:18.498Z
Chicago, IL – Happy National Fossil Day! Long before Chicago's skyscrapers, suburban neighborhoods and busy expressways, Illinois was home to enormous Ice Age mammals, tropical forests and creatures so unusual that scientists still debate what they were.
National Fossil Day was observed Wednesday, Oct. 14, celebrating the prehistoric discoveries that help explain Earth's ancient history.
According to the Illinois State Geological Survey and regional museum collections, Illinois contains fossils spanning hundreds of millions of years. Some of the most fascinating discoveries have occurred in communities residents recognize today.
Prehistoric Discoveries Across Illinois Glen Ellyn, DuPage County — The Perry Mastodon: On Oct. 16, 1963, workers excavating a pond on the property of federal Judge Samuel Perry discovered enormous prehistoric bones. Students and faculty from nearby Wheaton College helped recover the remains. The animal lived approximately 13,000 years ago, when mastodons roamed the region's forests. Its skeleton has been displayed at Wheaton College since 1973. Unlike mammoths, mastodons possessed distinctive pointed teeth suited for browsing woody vegetation.
Warrenville, DuPage County — The Blackwell Mammoth: On June 21, 1977, heavy equipment operator Gary Jones uncovered bones while digging clay near present day McKee Marsh in Blackwell Forest Preserve. Scientists eventually identified the remains as a woolly mammoth approximately 13,000 years old. About 75% of its skeleton was recovered. Remarkably, the surrounding clay preserved original bone material rather than fully mineralized fossils. The discovery attracted thousands of curious visitors, and the skeleton became an important part of the Forest Preserve District of DuPage County's educational collections.
Chicago, Cook County — Mammoth Remains Beneath the City: Historical accounts describe an 1880 discovery of prehistoric elephant remains during sewer excavation near present day Schiller Street. Workers reportedly uncovered a tooth, rib and tusk approximately 13 feet underground. The find illustrates how Ice Age remains can survive beneath modern urban landscapes, although details of the historic discovery warrant further archival verification.
Mazon Creek, Will and Grundy Counties — The Mysterious Tully Monster: Approximately 300 million years ago, northeastern Illinois contained tropical coastal environments teeming with unusual creatures. In 1958, amateur collector Francis Tully discovered a strange fossil with a flexible snout, toothed mouth and eyes positioned on a horizontal bar. Named Tullimonstrum gregarium, the creature became Illinois' official state fossil in 1989. Researchers have proposed competing explanations for its evolutionary relationships, including a possible connection to ancient vertebrates. Its classification remains disputed. Mazon Creek is also internationally recognized for exceptionally preserved jellyfish, insects, crustaceans, plants and prehistoric fish.
Saline County, Southern Illinois — A Buried Prehistoric Rainforest: Scientists studying coal mines near Galatia documented an extraordinary fossil forest approximately 307 million years old. Ancient trees and other plants were preserved in rock above coal seams, providing a detailed record of a vanished tropical ecosystem. The discovery helps researchers understand environmental changes that occurred long before dinosaurs appeared.
Chicago's Famous Dinosaur Has a Surprising History The Field Museum houses SUE, one of the most complete Tyrannosaurus rex skeletons ever discovered.
Found in South Dakota in 1990, SUE lived approximately 67 million years ago. The museum purchased the skeleton for $8.36 million at a 1997 auction following a complicated ownership dispute.
Although SUE wasn't discovered in Illinois, the dinosaur remains one of Chicago's most recognizable prehistoric attractions.
Where Residents Can Explore Illinois Fossils Families can learn more about the state's ancient past through Wheaton College's Perry Mastodon exhibit, the Forest Preserve District of DuPage County's Blackwell Mammoth collection, Chicago's Field Museum and the Illinois State Museum in Springfield.
From mastodons beneath Glen Ellyn to 300 million year old creatures preserved in Will and Grundy counties, Illinois' prehistoric history is far more remarkable than many residents realize.