Did a web search and found out both that certain cultivars are self pollinating, AND that the species are self pollinating.
More confused with that.

The hickories, and black walnuts,for that matter, have not received nearly so much study and research as their more economically-relevant relative, the pecan.
You *might* get some nuts with a single, solitary tree, but extrapolating from the pecan data and some of the BW stuff I've read, you really need at least two selections; not sure how pronounced dichogamy is with the hickories, but it's pretty stark in the pecan. Have seensome claims that hickory pollen is self-incompatible - don't know if that's the case, or if the difference intiming beween catkin pollen-shed and nutlet flower receptivity is such that they are unlikely to self-pollenize.
Pollen is wind-carried, so if there are other hickories in the area, they will get the job done. If you've got the space, I'd plant at least 2-3.