"counted slaves as 3/5 of a person"
Sigh...the 3/5 of a person was a compromise worked out between the Northern States that did not want to count slaves and the Southern States that wanted to fully count them.
http://www.government-and-constitution.org/us-constitution/three-fifths-compromise.htm
Free blacks in the both the North and South were counted as one person, not three-fifths. Learn some actual history and context instead of repeating statements taken of of context