The below link presents an excellent study on FPOC's and the laws governing them for the State of North Carolina prior to the Civil War.

Would it help to look at the Black Codes for each State due to differences in free vs slave populations by location....Section & State?

We totaled the FPOC Population from the Historical Census Browser for the Census Years 1830 & 1860. The breakout of FPOC's North vs South was quite interesting.

1830 FPOC's North......148,851 South.....158,653
1860 FPOC's North......239,760 South.....227,031

Art Thomas