IIRC, the largest cache of trilobites is found in the Genesee River gorge, Rochester NY. (But that may just be local).
I hunt where many fossils are present south of Rochester down to the southern tier of NY. No trilobites but encrustations of small clam shells and also soft body fossils in the shale from the Devonian period I tend to bring the best ones home. But they are all over.