Gunter,
Unfortunately, there probably aren't too many people here in Cinci who can help you out, but I can do my best for ya.
That area is one that typically hasn't had the best surveying, so it is tough to know what really is or isn't there.
The most common things around there (that county) are probably milks, rats, watersnakes, garters and ringnecks. There are records of copperheads from before the 1950s but nothing since. There are some more recent records of coppers from the county above that, but still pre75.
100 miles is a good range and would put you in copperhead range if you went SW as well as many of the other smaller snakes. Heading north would give you new species as well.
Here is a link to Ohio's Species list as well as laws.
http://www.ohiodnr.com/wildlife/PDF/pub03.pdf
Steubenville is kinda sitting on the border between the hill country of the SE and the till/lake plains of the N and W. For some of the more moutainous, or southernly species, you need to get down into the hills more. That being said, that seems to be a pretty nice spot for clear mountain streams coming in/out of West Virginia and Penn. Also, at that time of the summer, you might want to just do some poking around for mudpuppies or their larger cousin...
Good luck,
Jason
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www.buckeyeherps.com