Most African Americans in the US today are the descendants of slaves. The exceptions would possibly be the more recent emigrants or descendants of emigrants from Africa (though there was slavery in Africa, so some of these might well be descendants of slaves (as might most of the white Americans, as there was slavery in the Roman Empire and early Medieval times in Europe)).

In 1860, shortly before the American Civil War, and the emancipation of slaves, most blacks in America were slaves.

The free black population in the USA in the 1860 census was 476,748.

http://www.freeaainnc.com/censusstats1790-1860.pdf

This compares to the slave population in the same census of 3,950,528.

The total population of the USA in the 1860 census was 31,183,582

http://www.civil-war.net/pages/1860_census.html

225,926 free blacks were in the free states. 250,757 free blacks were in the slave states.

The states with the largest numbers of free blacks in 1860 were:

Maryland – 75,000

Virginia – 58,000

Pennsylvania – 57,000

New York – 49,000

Ohio – 37,000

North Carolina – 30,000

New Jersey – 25,000

Delaware – 20,000

Louisiana – 19,000

Indiana – 11,000

http://www.freeaainnc.com/censusstats1790-1860.pdf

Most of the free blacks in 1860 would have also been slaves or the descendants of slaves who were emancipated at some earlier point.

The population of blacks in America in 1860 who had no ancestors who were slaves would have been extremely small (if any).

There would be very few African Americans in the US today who did not have slaves among their ancestors.

(Of course, most white Americans would also have slaves in their ancestries, just many more generations ago. Most African Americans would have an ancestor who was a slave as recently as 1863 (emancipation declaration), or 1865 (13th amendment), which, (counting 25 years to a generation) is only 6 generations ago).