The largest Trilobite on display at the Smithsonian Natural History museum is from Ohio! Photo by Mike Rupert on Flickr (all rights reserved; used by permission).
Official State Fossil of Ohio
Ohio designated the Isotelus trilobite as the official state fossil in 1985. Pennsylvania and Wisconsin also recognize trilobites as state symbols. All State Fossils
Isotelus is the largest known trilobite; an extinct arthropod that lived between 430 and 480 million years ago when saltwater covered what is now the state of Ohio. Some Isotelus trilobites reached over two feet in length!
Source
