When Lake County Was Only A Puddle

Prehistory of Lake County


Henry Rowe, Feature Editor


Scale Model of a Dryptosaurus at the Dunn Museum of Lake County Photo provided by Henry Rowe

Natural history is too often ignored. While we pay more than enough attention to the history of our species, most traditional tellings of history leave natural history in the dust.

However, Lake county in its infancy would be unrecognizable to us. “Illinois was actually like a very shallow ocean, like a saltwater ocean. Which is why there’s a lot of deposits and things like limestone and sandstone here. Sandstone comes from the stand of the ocean, but as the plates begin to move over the span of millions and millions of years, that shallow warm ocean eventually dried up,” said Plaza.

However, Lake County would not remain lifeless for much longer. Roughly 420 million years ago the first Lake County residents appear in the area’s fossil record, during the height of the Silurian period. Most life in the early Silurian period was aquatic in nature. As Lake County was deep under the salty ocean waters, it became a hotbed for these early lifeforms.

By the Carboniferous period 300 MYA, the land that would become Lake County was a small part of a massive supercontinent called Pangea. During this time, Trees towering over 100 created massive forests home to early reptiles and amphibians.

These Reptiles evolved into the famous “terror lizards” or Dinosaurs we study today. Lake County was home to a wide array of dinosaurs, most notably the Dryptosaurus. Dryptosaurus, which lived in the late Cestecous, 67 MYA was nearly 25 ft tall. While Dryptosaurus and many other late cretaceous creatures populated Lake County, evidence of these beasts of a bygone age are unusually hard to come by in our county than elsewhere. “ As it was swampy, but later on it was completely dry. Think of it almost like the Sahara desert, where like all the wind and erosion is just pulling all that topsoil and other stuff away. That’s where all the dinosaur fossils would have been. So like, especially in the northern part of Illinois, there wouldn’t have been conditions allowing you to see a lot of fossils from that time” Said Plaza.

“Dinosaurs were everywhere. But, there’s very little evidence of that in Illinois, because after that the ocean dried up, but it had an effect on the fossil record. However, we have natural resources like coal and oil. You’d only find them because of that erosion. They call Chicago the Windy City, because it’s like the way that politicians in Chicago speak but, if you want to take it literally, you’d look back in prehistory. [Lake County was] a very windy area, and that has drastically changed a lot of the landscape is also why it’s pretty flat here as opposed to other places,” said Plaza.