Conversation so far:
What did James Black do?
James Black was an American knifemaker best known for his improvements to Bowie knife designed by Jim Bowie.
Why is the Bowie knife famous?
Jim Bowie had become famous for his use of a large knife at a duel known as the Sandbar Fight.
How many knives did James Black sell?
After Bowie's death in 1836, James Black did a brisk business selling his knives to pioneers bound for Texas. Everyone seemed to want Jim Bowie's knife.“
Besides the bowie knife what else was James Black famous for?
Did he have any family?
James Black was married to Anne Shaw.
What about any children?
James Black and his wife had three sons and a daughter.
Are there any other interesting aspects about James Black (blacksmith)?
There is a theory that James Black's legacy rests solely on Black's claims made well after he had been adjudged mentally incompetent.

Question: Why was he adjudged mentally incompetent?
Self-contained rewrite: Why was James Black (blacksmith) adjudged mentally incompetent?