The answer will depend on what you are trying to compare the number of blacks in the US with:the number of non-blacks in the USthe number of blacks living outside the US.
400,000
400'000
1000000
Most were living in the south, where there were half a million free blacks, and three and a half million slaves. There was no large black population in the northern states.
1000000
A lot less then there are whites.
There were a great many free blacks living in the south prior to the Civil War. Most free blacks in American lived in the south. In the 1860 census there were 30 million people in the US. Nine million were in the south, including three million slaves, and another half million free blacks. John Hope Franklin, the eminent black historian, has made the free black population of the south a subject of his excellent writing.
Approximately 135,000 free Blacks lived in the South when the US Civil War began.
13% of the American population was African-americans.
Whites, blacks, Hispanics, Jews and homeless people all living and working(not the homeless people) together in the country.
There was a lot of segregation in the South and many blacks were treated unfairly.