Cooooool. Captain Robert Smalls was the subject of my first-ever school research paper (with a BIBLIOGRAPHY, and CITATIONS 
), and I would love to see his story brought to life!
Unfortunately, it seems more and more common nowadays for screenwriters not even to bother attempting period-appropriate dialogue. Whether they’re convinced that modern audiences can’t understand the older communication styles, or whether they themselves just haven’t bothered to read enough historical writing to develop an ear for older styles, they seem to have mostly given up on trying to represent contemporary language in their characters’ speech.
I don’t want to hear 18th- or 19th-century characters talking like 21st-century people with occasional bursts of pseudo-period pomposity. I want a writer to put in the effort to learn how people—or at least fictional characters—of that time actually spoke, and to write plausible dialogue for people in that era. Such effort seems to be getting rarer and rarer, though.