Let me assume the role of 19th Century Language Police here. Although "Creole" may have a certain meaning in the U.S. now, that meaning is quite different from it's 19th Century meaning.
The word "Creole", derived from the Spanish word "Criollo" simply meant an individual of either race born in the New World.
My great-gradfather, born in Spain, was a "Peninsular". My grandfather, born in 1889 in Colonial Cuba, was a "Criollo". In Spanish colonies, this was a significant distinction as Spain tried to keep an iron grip on it's American colonies by limiting positions of power to Peninsulares. The effect, of course, was to foment revolution from both the Criollos and the Peninsulares with Criollo children.
The term used in 19th Century Louisiana for New World born free blacks was gens de couleur libre.
Wealthy whites of French and Spanish descent were also Creoles, and they did most of the dominating. Some people will blame "Yankees" for everything, but the decline of mixed race Creoles didn't come about until after Reconstruction. And considering how unrepresentative New Orleans was of the rest of the South before the 1890s, and how similar segregation was throughout the South, blaming the fall of the colored Creoles on Northerners looks like a stretch.
If you're far enough South, all problems come from the North, but for New Orleans the "North" included Mississippi, Arkansas and Baton Rouge, and the inspiration for segregation could be found in the antebellum slave codes and postbellum black codes more readily than in anything from farther North. The relevant distinction wasn't between North and South, but between Catholic New Orleans and Anglo-Saxon Protestant America. Within the South or the US, the position of people of mixed race in New Orleans was unique, but even there it was always precarious.