I saw a black squirrel while I was running at Prairie Oaks Metro Park West of Columbus (see video). I have seen many, many squirrels over the years most are gray or red. I have seen a few albino squirrels around OSU campus. I have only seen a few black squirrels over the years.
Black squirrels apparently can be mutations of gray squirrels. They are found in a number of areas in North America. They have been imported to Kent and Van Wert Ohio as well as Battle Creek Michigan (by the original Kellogg?). Black squirrels apparently have better cold tolerance and their dark color allows them to blend in better in dense forest. So why is one in Prairie Oaks? Either someone imported one (or more) to the park or it is a mutation of a gray squirrel. They are certainly striking and it will be interesting to see if more are seen.