On July 1, 1964, Otto Wilkosz was working on a sewer project in Western Springs, just alongside the Tri-State Tollway. Suddenly, he spotted what appeared to be unusually large bones in the excavation site. His fellow workers were about to put them back into the excavation when he decided to put them in the trunk of his car. A quick trip to the Chicago Natural History Museum confirmed his suspicions: the bones were from a prehistoric mastodon.
American mastodons were among the largest living land animals during the ice age. Compared to elephants and wooly mammoths, American mastodons were squatter, from 8 to 10 feet in shoulder height, and longer, about 15 feet. They weighed between 4 and 6 tons.
Examination of the 36-inch-long jawbone found by Wilkosz disclosed teeth that were as good as they were some 11,000 years (or more) before… each one three inches high and three inches wide.
Museum experts speculated that the creature found by Wilkosz had become trapped and died in what was a swampy area, now part of the Illinois Tollway’s right-of-way. And, while the bones were in remarkably good condition, they concluded that the previous Tollway construction had probably scattered the remaining parts of the skeleton, making a search for it virtually impossible.
Although exactly what caused the eventual extinction of Mastodons is unknown, they disappeared about the same time as native Americans began to populate the country, roughly 10,000 years ago. However, their fossils and remains have been found throughout the Midwest, as shown in the fourth illustration.
So, what became of Otto Wilkosz’ discovery? Unfortunately, at the time this occurred, the Field Museum was more interested in locating and preserving complete skeletons and did not want it for their collection. As a result, Wilkosz indicated that he would just probably “… clean and shellac it, and keep it around the house as a conversation piece.”