Oak Park in Cook County, Illinois — The American Midwest (Great Lakes)

Illinois Tulley Monster

Photographed by Sean P. Flynn, March 27, 2025

1. Illinois Tulley Monster Marker

Inscription.
300 Million Years Ago

Illinois is a coastal swamp, Illinois Tulley Monster

Erected 2012 by Park District of Oak Park.

Topics. This historical marker is listed in these topic lists: Animals • Anthropology & Archaeology • Parks & Recreational Areas.

Location. 41° 53.076′ N, 87° 48.113′ W. Marker is in Oak Park, Illinois, in Cook County. It is on South Marion Street near Pleasant Street, on the right when traveling north. The stone is a part of the labyrinth located on the western edge of Mills Park. Touch for map. Marker is at or near this postal address: 217 Home Avenue, Oak Park IL 60302, United States of America. Touch for directions.

Regionally, this marker is in Greater Chicago.

It is also in the American Midwest

and on the Great Lakes.

Globally, it is in North America,

the Western Hemisphere,

the Western World,

and the Anglosphere.

Historically, it finds itself in what was once the Viceroyalty of New France,

the territory of the Mississippian Culture,

and the Northwest Territory.

Other nearby markers. At least 25 other markers are within

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walking distance of this marker: Amphibians (here, next to this marker); The Age of Mammals (here, next to this marker); Ancient Illinois Climate (here, next to this marker); Sabre Tooth Tigers (here, next to this marker); Cambrian Sea (a few steps from this marker); Beginning of the Wisconsin Ice Age (a few steps from this marker); Volcanoes (a few steps from this marker); Oak Park Sand Spit (a few steps from this marker); Hunter Gatherers (a few steps from this marker); Solar System (a few steps from this marker); End of the Wisconsin Ice Age (a few steps from this marker); Oak Savanna (a few steps from this marker); Potowatamie (a few steps from this marker); First European Settlers in Illinois (a few steps from this marker); Mills Park Labyrinth (within shouting distance of this marker); Pleasant Home Foundation (within shouting distance of this marker); Mills Park and Pleasant Home (within shouting distance of this marker); The Kettlestrings (within shouting distance of this marker); Mills Estate Purchase (within shouting distance of this marker); Herbert S. Mills (within shouting distance of this marker); Village of Oak Park (within

Mills Park Labyrinth image. Click for full size.

Photographed by Sean P. Flynn, March 27, 2025

2. Mills Park Labyrinth

shouting distance of this marker); Pleasant Home (within shouting distance of this marker); a different marker also named Mills Park and Pleasant Home (about 300 feet away, measured in a direct line); a different marker also named Mills Park and Pleasant Home (about 400 feet away); a different marker also named Mills Park and Pleasant Home (about 500 feet away). Touch for a list and map of all markers in Oak Park.

More about this marker. The stone is one of about 20 pavers in Mills Park that show the history of Oak Park from the dawn of the solar system through 2012. The pavers are part of a labyrinth embedded into the ground near the western entrance into Mills Park.

Regarding Illinois Tulley Monster. The tulley monster (usually spelled Tully; Tullimonstrum gregarium) was designated the state fossil of Illinois in 1989. It was named after a fossil hunter, Francis Tully, who discovered the fossil near Braidwood, Illinois in 1955.

Related marker. Click here for another marker that is related to this marker. The Mills Park Labyrinth marker page includes a list of all 21 stones in the labyrinth in chronological order

Also see . . . Illinois State Fossil - Tully Monster.

Photographed by Sean P. Flynn, March 27, 2025

3. Mills Park labyrinth

Excerpt: "In 1955, a fossil hunter by the name of Francis Tully was exploring the spoil piles of a coal mine near Braidwood, Illinois. He was searching for fossils inside of 300 million year old ironstone nodules found in the Francis Creek Shale. Mr. Tully split one open to reveal something a very strange animal that no one had seen before. It had a long proboscis or snout on its head sporting a claw, spade-shaped fins on its rear and a horizontal bar underneath its head with an eye on each end. This prehistoric oddity would eventually be named Tullimonstrum gregarium (commonly referred to as a Tully Monster) and it would go on to confound scientists for decades.

"In the decades since its original discovery hundreds of additional specimens have been found in Illinois, some up to 14 inches long. In 1989 this enigmatic animal was declared the Illinois state fossil which is quite fitting as Illinois is the only location in the world similar animals have been found."

(Submitted on March 29, 2025, by Sean P. Flynn of Oak Park, Illinois.)

Photographed by Sean P. Flynn, March 27, 2025

4. Mills Park labyrinth

A nearby historical marker says that the labyrinth's artistic style was inspired by the architect George W. Maher, who designed the Pleasant Home, located in this park.

Credits. This page was last revised on March 31, 2025. It was originally submitted on March 29, 2025, by Sean P. Flynn of Oak Park, Illinois. This page has been viewed 105 times since then and 11 times this year. Photos: 1, 2. submitted on March 29, 2025, by Sean P. Flynn of Oak Park, Illinois. 3, 4. submitted on March 27, 2025, by Sean P. Flynn of Oak Park, Illinois.