This is what my master's thesis was on, so buckle in, I love to talk about it. It was specifically about a wealthy Tuscaloosa, Alabama man named Solomon Perteet. He was by no means the most successful person of color in the antebellum South, but he's the one I know best. That said, let me give you a short bio of his life, before I move into what the literature as a whole says about your question.

Solomon was born in 1789 to a wealthy white woman in Georgia. His father was most likely a slave, based on the sparse population data that survived the War of 1812. He was raised by his mother, and was apprenticed to a wealthy plaster worker at the age of eleven. He moved to Tuscaloosa in the mid 1820s, and received a lucrative contract to do the plaster work in the new Tuscaloosa capitol building.

He was already a slave owner by the time he arrived in Alabama, and married one of his slaves, Lucinda, soon after his arrival. He petitioned and paid for manumission for Lucinda and their eldest child, Andrew Jackson. (Interestingly, Solomon also paid for the manumission of Lucinda's son from another relationship, but he was only to be freed when he turned 21.)

Solomon branched out into real estate, partnered with a white man to open a tannery, kept a medium-sized farm, owned a store, and got into money lending. He did most of his business with white clients, and successfully took debtors to court when they were unable to pay him back. I even found multiple instances of Lucinda appearing in court on his behalf, with an equally impressive success rate! As to the scale of his holdings, he owned at least forty city lots (10 city blocks), several rural plots of land, and large reserves of specie. According to English geologist (and Darwin's mentor!) Charles Lyell, Perteet loaned 17,000 dollars to a debtor who was unable to repay the money, and Solomon emerged relatively unscathed by the loss. Lyell traveled to the South in the 1840s and wrote about his trip, including meeting Solomon in Tuscaloosa.

Socially, his family was well-integrated into elite white society. The Perteet family lived in the most fashionable neighborhood in town. They had their own pew at the Episcopal church, and held weddings, baptisms, and funerals in the white sanctuary, while also retaining access to the black chapel. Solomon, Lucinda, two of his children, and two of his grandchildren, are buried in Greenwood Cemetery, right in the middle of his rich white neighbors. After his grandchildren were orphaned in 1869, they were informally adopted by a former CSA officer, lived in a mansion, and were sent to college.

That said, racism was still fundamental to the legal and social order of the South. In my work, I found two boundaries that Solomon was unable to cross, even with his substantial wealth. The first is a concrete one. He was unable to have his son admitted to the University of Alabama in the early/mid 1840s. I have no evidence of social pressure in either direction, but there were laws expressly prohibiting higher education for people of color at the time.

The second barrier was an intangible one. Solomon was unable to escape from the the conflation of blackness with poverty and servitude in public discourse and consciousness. Even though Solomon bought his wife and daughters $300 silk dresses, silk gloves, and velvet cloaks, ads for "negro clothes" ran in the paper. Lucinda's glowing obituary ran in the same 1869 Tuscaloosa Monitor that bore the headline, "Lo, the lazy negro."

This is probably a bit of a jumble; I've been working on it off and on today. However, this is my take on the boundaries of race and class in the Old South, based on my own research. Once I post this, I'll post a follow-up comment giving you a rundown of the literature.

This as incredibly helpful. I'm doing my master's thesis on the historical memory of free black societies in the north. Could you suggest anything worth reading on that subject?