The copepods are a large and diverse group consisting of several orders. Ohio EPA does not report any copepods in their Aquatic Macroinvertebrate List (2019).
Reid (2016) lists a number of species recorded from Ohio, which are listed in the Checklist in the horozontal bar above. This may not be a totally inclusive list, however, as many are listed "North America," "Great Lakes," or in neighboring states.
Boehler and Krieger (2012) conducted an extensive study of copepods of the Old Women's Creek State Nature Preserve and list several additional taxa. Their atlas gives excellent discription and pictures of copepods.
The keys in Smith (2001) and Reid (2016) will suffice to identify the copepods of Ohio.
A useful introductory site for recognizing the copepods is the University of New Hampshire, Center for Freshwater Biology's Image Based Key to Zooplankton of North America (cfb.unh.edu).