Douglas Deal wrote, "A final point about VA/NC differences re manumission 
policies and practices. It may have been more difficult for NC owners to 
free their slaves than it was for VA owners (in the decades after the 
Revolution),
but there were roughly the same numbers of free blacks (proportionally)
in these two states in 1790 and 1810. The census figures presented by
Ira Berlin in Many Thousands Gone (p.372) indicate that 5% of all NC
blacks were free in 1790 and 6% in 1810, while the comparable VA
percentages were 4% in 1790 and 7% in 1810. In absolute terms, the
number of NC free blacks had increased in that 20-year period by a
factor of a little more than 2, while VA free blacks had increased by a
factor of around 2.5. The difference is of some significance, of course,
but is not quite as extreme as suggested by Paul Heinegg in his posting."

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Hi Douglas. Free African Americans in North Carolina were all mixed-race and 
nearly all came to North Carolina from Virginia during the colonial period 
when North Carolina was desperate for settlers. The increase was almost all 
natural. Later, entry of freed slaves from Virginia or any other state was 
forbidden. Many had left by the Civil War and those that remained, in many 
cases very light-skinned and culturally white, were not really considered 
former slaves.
Paul