In the middle of Desperado #8 (1949), there was a double-page spread announcing that next issue, the title would be changing it's name, and getting a new star (click to embiggen):
So who the hell is the Black Diamond?
Bob Vale's parents were killed in in a massacre of white settlers by Native Americans which was instigated by an evil white man. Later, his adoptive father is killed by the same guy--take that, Batman, even Joe Chill didn't kill two sets of your parents!
So, to protect his girlfriend and all his friends, he puts on a mask and fights crime. Just like every other Western hero (ahem).
Does he even have an office? How do people get in touch with him when they need help? What about all the paperwork the job requires? Does he have body cameras? What if he's really evil, and just clearing out the competition? What about...
From Desperado #8 (1949) and Black Diamond #9 (1949)