Not totally unknown, but:
Anything regarding The Red Tails, also known as The Tuskegee Airmen. They flew from beginning to end of WWII.
So many stories of them I haven’t heard.
Also CNN? did a special on the Tulsa Race Massacre of 1921, of which I was only vaguely aware.
Here’s some pretty unknown local history (every Northern city has a similar tale). Sugar Hill.