As I recall, one of the hardware stores in Cornelius-Hillsboro are had black powder and accessories in stock. You'll have to call around.
As for making black powder, don't do it! There is a reason black powder mills are always located in buildings away from anything important, and operated by nervous people.
To properly make black powder, you have to grind the materials, and corn them. This involves wet (with alcohol) powder, static electricity, and machines. BTW, you get different burn properties depending on what the grain size is. Did you just make FFFG or FG powder?
Making black powder is like making match heads, it might be a fun chemistry experiment, but people tend to get POed when you burn down the neighborhood.
If you are dead set on going ahead, make sure you have enough liability insurance to protect you from the following lawsuits. BSW